Shooting .223 in a 5.56 rifle


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Angleiron
December 2, 2009, 01:09 PM
I bought my 5.56 because of the versatility of being able to shoot both types of rounds in a pinch, and was wondering if anyone else is shooting .223 in their 5.56 rifle? I know that it is not as accurate as a shooting these rounds out of a designated .223 rifle, but how much of a difference is there? I have the opportunnity to get 1000 rounds of .223 for a real good price, but if it is a big difference then maybe it is not worth it.

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TexasRifleman
December 2, 2009, 01:10 PM
Accuracy wise I've never been able to tell any difference.

I mean, if it's surplus junk 5.56 I'm shooting maybe, but in general I never notice enough difference to worry about for every day shooting.

stacks04
December 2, 2009, 01:17 PM
accuracy should not suffer either.

mongoose33
December 2, 2009, 01:19 PM
I bought mine in 5.56 for the same reason; I don't notice any difficulties.

rcmodel
December 2, 2009, 01:24 PM
There is more variety of accurate .223 loaded by the factories then there is 5.56.

Most of the 5.56 is loaded with FMJ-BT GI style bullets.
And none of them will prove to be as accurate as any of the .223 match or varmint bullet loads.

As for best accuracy?
Your chance of best accuracy in a 5.56 chambered gun is .223 match or varmint ammo.
Followed by, or equaled by 5.56 Match ammo.

5.56 FMJ-BT will be at the very bottom of the accuracy heap in either chamber in any gun.

rc

wishin
December 2, 2009, 01:36 PM
As I understand it, the .223 has a tighter chamber around the neck and is shorter which purportedly allows for a little more accuracy. RRA's Wylde chamber is supposed to "correct" this so .223 and 5.56 are equally as accurate.

Boba Fett
December 2, 2009, 01:41 PM
I bought mine in 5.56 for the same reason; I don't notice any difficulties.
Same.

No issues and accurate enough as far as I can tell. If I want more accurate I'll get a bolt gun and use match ammo.

W.E.G.
December 2, 2009, 04:32 PM
.223 ammo is OK in 5.56 barrel.

5.56 ammo is not OK in .223 barrel.

This was reported in the American Rifleman magazine recently.

.223 chamber is "smaller" than 5.56 chamber.

http://i227.photobucket.com/albums/dd7/rkba2da/rifle%20pics/AR-15/556-223chambercomparison.gif

.223 Remington vs. 5.56: What’s In a Name


By BRYCE M. TOWSLEY field editor
American Rifleman – September 2007


Most gun guys know the history of the .223 Remington and that it - like so many of our popular cartridges - started life in the military. Because the military switched to metric designations sometime in the 1950s, this little .22-cal. cartridge was later called the 5.56x45 mm NATO (commonly referred to as "5.56x45 mm").

The 5.56x45 mm surfaced in 1957 as an experimental cartridge in the AR-15 rifle. The concept was to develop a smaller, lighter military cartridge that would still be traveling faster than the speed of sound at 500 yds., and this was accomplished by using a 55-gr. boattail bullet. The AR-15 evolved into the select-fire M16 rifle that was adopted by the military in 1964.

Even though it would ultimately kill off its own .222 Rem. and .222 Rem. Mag. cartridges, Remington was quick to act, and very shortly after the military adopted the 5.56x45 mm cartridge the firm brought out the civilian version, called the .223 Remington. Confusion followed.

The common misconception is that the two are the same; that 5.56x45 and .223 Rem. are the same dance partner, but with a different dress. This can lead to a dangerous situation. The outside case dimensions are the same, but there are enough other differences that the two are not completely interchangeable.


One big difference is pressure. It becomes a bit confusing, as the pressure for the two is not measured in the same way. The .223 Rem. is measured with either Copper Units of Pressure (c.u.p.) or -- more recently -- with a mid-case transducer in pounds-per-square-inch (p.s.i.). The military 5.56x45 mm cartridge is measured with a case mouth transducer. The different measuring methods prevent a direct comparison, as a case mouth transducer gives lower numbers on identical ammunition when compared to those from a midcase transducer. That's because the pressure is measured later in the event, after the pressure has already peaked. According to Jeff Hoffman, the owner of Black Hills Ammunition, military ammunition can be expected to hit 60,000 p.s.i., if measured on a Sporting Arms and Ammunition Manufacturers' Institute (SAAMI) mid-case system. Black Hills loads maximum average pressure is 55,000 p.s.i., while a 5.56x45 mm measured with a case mouth transducer has a maximum average pressure of 58,700 p.s.i.

While the 5.56x45 mm chamber is slightly larger than the .223 Rem. chamber in just about every dimension, the primary difference is throat length, which can have a dramatic effect on pressure. The 5.56x45 mm has a longer throat in the chamber than the .223 Rem. The throat is also commonly called the leade, which is defined as a portion of the barrel directly in front of the chamber where the rifling has been conically removed to allow room for the seated bullet. Leade in a .223 Rem. chamber is usually 0.085", while in a 5.56x45 mm chamber the leade is typically 0.162", or almost twice as much as in the .223 Rem. chamber. Also, the throat angle is different between the two chambers, and that can affect pressure rise and peak pressure.

SAAMI regulates cartridge overall length, but not bullet ogive design. The shape of the ogive can significantly affect how far the bullet jumps before contacting the rifling. Some 5.56 mm bullets have an ogive suitable for 5.56 chambers with the longer throat, but if they were chambered in a .223 Rem., it could result in very little, if any, "jump" to the rifling. This can increase pressures. Remember, the 5.56x45 mm already starts out at a higher pressure. If the higher-pressure 5.56x45 mm cartridge is then loaded into a .223 Rem. firearm with a short throat, the combination of the two factors can raise chamber pressures.

If you are a handloader, you must also consider that the 5.56x45 mm cartridge case may have a thicker sidewall and a thicker head, which were designed to withstand the stresses generated by the higher chamber pressures. This reduces the powder capacity of the case. If the 5.56x45 nun case is reloaded with powder charges that have proven safe in .223 Rem. cases, this reduced internal capacity can result in much higher chamber pressures.

Bottom line? It is safe to fire .223 Rem. cartridges in any safe gun chambered for 5.56x45mm. But, it is not recommended and it is not safe to fire 5.56x45 nun cartridges in a firearm chambered for .223 Rem.

In fact, the 5.56x45 mm military cartridge fired in a .223 Rem. chamber is considered by SAAMI to be an unsafe ammunition combination and is listed in the "Unsafe
Arms and Ammunition Combinations" section of the SAAMI Technical Correspondent's Handbook. It states: "In firearms chambered for .223 Rem. - do not use 5.56x45 mm Military cartridges."

There is no guarantee, however, that .223 Rem. ammunition will work in 5.56x45 mm rifles. Semiautomatic rifles chambered for 5.56x45 mm may not function with .223 Rem. ammunition because they are designed to cycle reliably with the higher pressure and heavier bullets of the 5.56x45 mm particularly with short barrels. While problems are rare, they do not indicate that the ammunition or rifle are defective. Like some marriages, they are simply incompatible.

When shooting .223 Rem. cartridges in a firearm chambered for 5.56x45 mm, it's likely that there will be a degradation in accuracy and muzzle velocity due to the more generous chamber dimensions. That's not to say that a firearm chambered in 5.56x45 mm won't be accurate with .223 Rem. loads, only that, on average, the .223 Rem. chambered firearms will be more accurate with .223 Rem. ammunition than rifles chambered for 5.56x45 mm firing .223 Rem.

Another issue is the twist rate of the rifling. The SAAMI specification for .223 Rem. is a 1:12" twist, and most non-AR-15-type rifles will use that rate. But, this is a cartridge that crosses a wide spectrum of uses, and as a result there is often a wide deviation from the 1:12" twist rate, particularly in the very popular AR-15-style "black guns." There are bullets available for the .223 Rem. that range in weight at least from 35 grs. to 90 grs. With that wide of a spectrum, one twist rate is not going to be enough.

Firearms chambered for 5.56x45 mm often have a rifling twist rate of 1:7" to stabilize the long, sleek, heavy bullets used in long-range shooting. Any rifle with a 1:7" twist rate will work best with bullets heavier than 60 grs.

On the other hand, a 1:12" twist rate (most bolt-action .223 rifles) will stabilize most bullets up to 60 grs., however some longer 60-gr. bullets will not shoot well with that twist rate. Many firearms use a 1:9" twist, which is a very good compromise that works well with most bullets up to 70 or 75 grs. The great thing is that if you have a good barrel and quality bullets, the 1:9 works well with even the lightest bullets.
What does all this mean? If you have anAR-15 type firearm with a 5.56x45 mm chamber you can shoot either .223 Rem. or 5.56x45 mm safely. If your twist rate is 1:7" you should use bullets weighing 60 grs. or heavier. If you have any rifle with a 1:12" twist you should shoot bullets of 60 grs. or less for best accuracy. If you have a .223 Rem. rifle of any type, it is not recommended that you use 5.56x45 mm ammunition.

McBuck
December 2, 2009, 06:03 PM
So...what is the chambering for a new 580 Mini-14, when the owners manual and the stamping on the gun says ".223 or 5.56" ? Ruger says the gun will accept 5.56. I have no reason to doubt that. I will probably only ever use .223 but what if I ever need/have the opportunity to use 5.56 ?


Great thread by the way ! Informative.

TexasRifleman
December 2, 2009, 06:07 PM
Mini-14's have always been 5.56 chambers, I don't believe that has changed with the new models. Their engraving a novel on the side of the rifle seems to get worse every year though :)

sandkicker
December 2, 2009, 06:40 PM
I hate to have my first post on this forum to be a disagreement, however:

Re: "Mini-14's have always been 5.56 chambers"

Should read "Mini-14's made since 1986 have 5.56 chambers"

SaxonPig
December 2, 2009, 06:40 PM
Once again, #32 covers this VERY popular topic.


223 vs. 5.56 (and .308 vs. 7.62x51).

32. There is essentially no difference between commercial .223 and military 5.56 ammo. The same is true with .308 and 7.62 ammo. The military stuff has slightly thicker brass with a tiny bit more length in the shoulder and I hear this is for strength when feeding through full-auto guns that tend to slam the rounds into the chamber violently. But otherwise, there doesn’t appear to be any difference that I have noted after many years of shooting both military and commercial ammo through my .223 and .308 rifles, both bolt action and semi-auto although with some guns with tight chambers closing the bolt on military ammo can be a bit snug. The military 5.56 ammo is loaded to very slightly higher pressures than commercial .223.

Maverick223
December 2, 2009, 07:21 PM
Should read "Mini-14's made since 1986 have 5.56 chambers"I am pretty sure that is not true either, as I believe the "target" model is chambered for .223, and 5.56 is not recommended.

:)

Boba Fett
December 2, 2009, 07:29 PM
It is a popular misconception that military 5.56 ammo is loaded to higher pressures than commercial .223 but it is not.


And yet SAAMI's site says it is unsafe and not to use 5.56 in a 223.

http://www.saami.org/Unsafe_Combinations.cfm


Fulton Armory doesn't think it's really a good idea either:
http://www.fulton-armory.com/556-vs-223-Chambers.htm
Here's the problem. Many NATO cartridges have bullets that will become jammed into the rifling of a SAAMI chambering (the throat is too short). This is VERY DANGEROUS, for a great number of reasons.

From Winchester:
http://web.archive.org/web/20080505215048/http://www.winchester.com/lawenforcement/news/newsview.aspx?storyid=11
Paul Nowak
5/4/2001
.223 Rem VS 5.56mm

There are a lot of questions about these two cartridges. Many people think they are identical - merely different designations for commercial and military. The truth is that, although somewhat similar, they are not the same and you should know the differences before buying either cartridge.

* The cartridge casings for both calibers have basically the same length and exterior dimensions.
* The 5.56 round, loaded to Military Specification, typically has higher velocity and chamber pressure than the .223 Rem.
* The 5.56 cartridge case may have thicker walls, and a thicker head, for extra strength. This better contains the higher chamber pressure. However, a thicker case reduces powder capacity, which is of concern to the reloader.
* The 5.56mm and .223 Rem chambers are nearly identical. The difference is in the "Leade". Leade is defined as the portion of the barrel directly in front of the chamber where the rifling has been conically removed to allow room for the seated bullet. It is also more commonly known as the throat. Leade in a .223 Rem chamber is usually .085". In a 5.56mm chamber the leade is typically .162", or almost twice as much as in the 223 Rem chamber.
* You can fire .223 Rem cartridges in 5.56mm chambers with this longer leade, but you will generally have a slight loss in accuracy and velocity over firing the .223 round in the chamber with the shorter leade it was designed for.
* Problems may occur when firing the higher-pressure 5.56mm cartridge in a .223 chamber with its much shorter leade. It is generally known that shortening the leade can dramatically increase chamber pressure. In some cases, this higher pressure could result in primer pocket gas leaks, blown cartridge case heads and gun functioning issues.
* The 5.56mm military cartridge fired in a .223 Rem chamber is considered by SAAMI (Small Arm and Ammunition Manufacturers Institute) to be an unsafe ammunition combination.



Before buying either of these two types of ammunition, always check your gun to find what caliber it is chambered for, then buy the appropriate ammunition. Most 5.56mm rounds made have full metal jacket bullets. Performance bullets - soft points, hollow points, Ballistic Silvertips, etc. - are loaded in .223 Rem cartridges. Firing a .223 Rem cartridge in a 5.56mm-chambered gun is safe and merely gives you slightly reduced velocity and accuracy. However we do not recommend, nor does SAAMI recommend, firing a 5.56mm cartridge in a gun chambered for the .223 Rem as the shorter leade can cause pressure-related problems.



So, yes...you can shoot 223 from 5.56, but shooting 5.56 from 223 is unwise and possibly dangerous.

Now, some people may shoot 5.56 from 223 and not have issues...yet.

I just wouldn't want to be the one person that proves why manufacturers and organizations warn against it.

SaxonPig
December 2, 2009, 10:32 PM
Case dimensions are identical. I have shot hundreds of military 5.56 through several commercial bolt and semi-auto rifles without incident. That's all I know.

http://stevespages.com/jpg/cd223remington.jpg

http://stevespages.com/jpg/cd556nato.jpg

I did make a slight correction. The military ammo is loaded a tad hotter. I doubt it's enough to make a difference. Yes, the SAAMI lawyers tell them to say using 5.56 in a .223 is unsafe. All reloads are unsafe, too, you know.

wishin
December 3, 2009, 06:56 PM
I am pretty sure that is not true either, as I believe the "target" model is chambered for .223, and 5.56 is not recommended.

My target model is marked .223 caliber on the receiver.

Maverick223
December 3, 2009, 09:18 PM
My target model is marked .223 caliber on the receiver.How does it shoot? I get the feeling that despite the target name it still isn't a bench gun. Not trying to bash them (don't know about the target variant, but the new ones are much improved over the former series), as I rather like the Mini, just wondering.

:)

wishin
December 3, 2009, 09:25 PM
I've been very pleased with the groups using 68 gr. Ultramax. Getting consistent 3/4' 3 shot groups from a bench rest with bipod, with an occasional flyer. I tried many different factory brands and various bullet weights. It loves the Ultramax loads.

Maverick223
December 3, 2009, 09:47 PM
Not bad at all, glad to hear that it shoots well. You need to post a group in Krochus' Mini Match...you might just win. ;)

EDIT: In case you're interested, Here (http://www.thehighroad.org/showthread.php?t=485140) is a link to the match.

possum
December 4, 2009, 07:49 AM
welcome to thr.

for the type of training i do and in the context of which i train with my ar, the accuracy difference if there is one is not somthing that i am worried about, and honestly something that i have never had an issue with.

Offfhand
December 4, 2009, 08:55 AM
Just curious, has anyone ever heard of 5.56 ammo causing problems in a .223 Rem bolt rifle?

rcmodel
December 5, 2009, 12:56 PM
Yes, I have.

Many years ago, SAKO made some Vixen's with .223" bores instead of .224".
They were also tight chambered in .223 Rem.

Along the same time, Remington was making .223 Rem Model 40-X target rifles with very tight .223 Rem match chamber dimensions.

There were reports of blown primers in both guns when shooting higher pressure 5.56 ammo in them.
No harm was done to the shooters.

That is the only two instances I have ever heard of.

I hate to have my first post on this forum to be a disagreement, however:
Re: "Mini-14's have always been 5.56 chambers"
Should read "Mini-14's made since 1986 have 5.56 chambers" I hate for you to be wrong too, but you are.

All Mini-14's, since day one, have been chambered for .223 and 5.56.
It says so in the owners manual.

Mini-14 Series 180 1974 - 1977.
http://www.ruger-firearms.com/products/_manuals/mini14-180.pdf

The only exception is the current Target model which is chambered for .223 only.

rc

greyling22
December 5, 2009, 06:34 PM
so if I took 5.56 brass and reloaded it in a .223 die set with .223 load data (not a hot load, just a middle range one) would it be safe to shoot in a .223 chamber?

Maverick223
December 5, 2009, 09:41 PM
so if I took 5.56 brass and reloaded it in a .223 die set with .223 load data (not a hot load, just a middle range one) would it be safe to shoot in a .223 chamber?I don't see why not, and it should last a little longer than .223 brass. Furthermore, I have never heard of or seen "5.56 dies", as the case is identical (with exception of thickness). I can tell you that .223 dies work just fine for my 5.56 (brass and rifle).

:)

Boba Fett
December 5, 2009, 09:47 PM
so if I took 5.56 brass and reloaded it in a .223 die set with .223 load data (not a hot load, just a middle range one) would it be safe to shoot in a .223 chamber?


From post 14:
The 5.56 cartridge case may have thicker walls, and a thicker head, for extra strength. This better contains the higher chamber pressure. However, a thicker case reduces powder capacity, which is of concern to the reloader.

Other than that I don't see any reason it wouldn't work.

Mags
December 5, 2009, 09:57 PM
If a 5.56 case is thicker than 223 brass how can a 223 bullet fit in a 5.56 case?

wishin
December 5, 2009, 10:18 PM
I believe both use a .224 diameter bullet.

Maverick223
December 5, 2009, 10:29 PM
If a 5.56 case is thicker than 223 brass how can a 223 bullet fit in a 5.56 case?I don't believe that the thickness at the neck is any different from the .223, and the bullet diameter is definitely the same (.224).

:)

chuckusaret
December 5, 2009, 10:36 PM
Hey guys, SAAMI has been saying since the late 1970's not to use 5.56 in weapons marked .223 only and I take their word and don't do it.

SAAMI info: http://www.thegunzone.com/556v223.html

wishin
December 5, 2009, 10:47 PM
Post#8 by W.E.G. in this thread, does a good job of explaining the differences and interchangeability.

BrianB
December 5, 2009, 11:11 PM
I shoot both with zero problems. Accuracy is not noticeably different, but then again, I'm not competing for match accuracy anyway. I'm told that my 5.56 ammo is louder than my .223 ammo. From behind the barrel, with ear protection, I can't tell.

Bottom line is to get a 5.56 chamber. Then you're completely fine.

Maverick223
December 5, 2009, 11:37 PM
Edited post 28 to read: "...don't believe that the thickness at the neck is any different...", mistakenly said that the neck was of a different thickness.

:)

greyling22
December 5, 2009, 11:40 PM
I was just asking because I still had a few 556's loaded as 223's and didn't know if it was safe to shoot them in my new 223 bolt gun. sounds like I am good to go.

Maverick223
December 5, 2009, 11:47 PM
sounds like I am good to go.With a .223 chamber (such as yours) I am not positive, but I believe you will be fine. With a 5.56 chamber (such as the O.P.) I know you're safe with 5.56 and .223, as well as 5.56 resized using .223 dies.

:)

Kurt_D
December 6, 2009, 12:26 AM
223 vs. 5.56 (and .308 vs. 7.62x51).

32. There is essentially no difference between commercial .223 and military 5.56 ammo. The same is true with .308 and 7.62 ammo. The military stuff has slightly thicker brass with a tiny bit more length in the shoulder and I hear this is for strength when feeding through full-auto guns that tend to slam the rounds into the chamber violently. But otherwise, there doesn’t appear to be any difference that I have noted after many years of shooting both military and commercial ammo through my .223 and .308 rifles, both bolt action and semi-auto although with some guns with tight chambers closing the bolt on military ammo can be a bit snug. The military 5.56 ammo is loaded to very slightly higher pressures than commercial .223.

I don't know what you consider "slightly" but in the case of 5.56 NATO vs. .223 from AR w/ 20" 5.56 chambered barrel the 62gr .223 loads clock in at ~3000fps while M855 clocks in at ~3200fps. I haven't chronoed it yet but M193 should clock in at 3300+ fps from a 20" barrel while 55gr .223 normally clocks in at 3200 fps from a 24" barrel. That's a very big slightly.

7.62 NATO and .308 are the opposite so far as max pressures are concerned but I don't think there's much difference here commerically unless you get into the hot and heavy or handloaded .308 loads. If you where to beleive the reloading manuals though a 150gr bullet can be pushed to 2900fps when hitting max .308 pressures while typical 7.62 NATO loads clock in at what 2700fps?

You also have to look at, in the case of .223/5.56, what's using what chamber? Semi-autos typically use 5.56 chambers (or a version of) while bolt guns typically use .223 chambers. It's pretty well known that gas guns usually show pressure signs sooner than bolt guns and that bolt guns are usually stronger action wise. I doubt other than a hard to extract case every once in a while it would matter much to fire 5.56 in a .223 chambered modern bolt gun.

With 7.62 and .308, I wouldn't run some hot and heavy .308 loads through a mil surp 7.62 gun. I think this is a more dangerous situtation because the rolls are reverse and the semi-auto is getting the higher pressure ammo. Add that to the fact that mil surps are usually older guns not designed for anything near what we can load today. Now their newer decendants such as new DSA FAL, PTR-91, M1A, AR-10, etc. I doubt there's much issue.

SpeedAKL
December 6, 2009, 12:33 AM
High quality factory .223 will out-shoot 5.56 milsurp with boring regularity so whatever minute accuracy differences there may be in shooting SAAMI .223 out of a 5.56 chamber will be more than made up for.

The only military issued ammo that will approach civilian .223 match loads is the Mk.262 ammo that SOCOM has been known to use. This is loaded with the 77-gr sierra match king bullet. A very similar load is available through Black Hills.

dogngun
December 6, 2009, 08:25 AM
Chambers are usually a little larger in military rifles to allow for slight variations in ammo, dirt, etc, and the brass is slightly thicker, and primers slightly harder.

I doubt there is much other difference.

mark

SaxonPig
December 6, 2009, 09:55 AM
Kurt D

I looked up the chamber pressures and they were like 2,000-3,000 PSI greater on the 5.56. That's not really a whole lot (maybe 4% or so) and is probably mostly due to the thicker case on the military rounds. I would not be surprised if the ammo manufacturers used the same powder charge for commercial 223 and military 5.56 but the cases for each are different in thickness causing the slightly elevated pressure in the military rounds. Most reloading manuals warn to reduce reloads slightly with military cases due to the added thickness raising pressures a tad.

Of course gun makers and ammo makers issue the usual dire warnings on advice of their lawyers. But like I said, I have used commercial and military ammo interchangeably in my 223 and 308 rifles, both auto and bolt, without any issues. I have never HEARD of anyone having any sort of problem.

An early 223 rifle made before the advent of the longer 68 grain bullet might be a concern due to lack of free-bore with such ammo, but I think recently made rifles have enough chamber length to use them. You always want to be aware of overall cartridge length in any rifle.

Offfhand
December 6, 2009, 10:35 AM
REMODEL, thanks for getting back with response to my question. It's easy to understand why the Sako would have a pressure problem, not just with 5.56 Mil ammo but with standard .223 as well. The same with the 40-X if it has a BR dedicated chamber and neck specs. The Remington custom shop BR neck is .246" unless specified otherwise by customer. This requires turning the case necks to .010" for ample, yet close fit. Standard neck diameter of 5.56 and commercial .223 ammo averages close to .248." Which makes it difficult to force into a BR chamber, requiring a hard, determined push on the bolt to get it closed, if at all. A squeeze that tight would certainly result in blown primers, etc. with any otherwise standard 5.56 or .223 load. But in both examples the situations described would seem to be more related to non-standard chamber or barrel specs. Where I work we have a number of "slave" .223 Cal rifles used for evaluating 5.56 Mil and .223 commercial loadings. These have standard SAAMI chambers and I'm not aware of there having been any problems. Which is why I'm trying to get reports from outside observers such as yourself. Thanks again

happygeek
December 6, 2009, 11:32 AM
Wait, the SAAMI unsafe combinations linked to (http://www.saami.org/Unsafe_Combinations.cfm) says that a 9mm Luger (Parabellum) chamber is unsafe with 9mm NATO (Military) :confused:

I thought that 9x19mm Luger, aka Parabellum, was 9mm NATO. I'll have to Google this now. At any rate, the only 9mm I own is a Beretta 92FS and I'm pretty sure it's 9mm NATO.

rcmodel
December 6, 2009, 12:49 PM
Same difference.

9mm NATO is loaded to higher pressure then American SAAMI standard pressure 9mm Luger.

It's more like +P SAAMI spec ammo I suppose.

Whatever it is, your Beretta 92, and most all other 9mm pistols with a military design background were made to shoot it.

As for .223/5.56 pressure comparisons?
Can't do it, because the military testing measures pressure in a different place in the barrel then SAAMI specs call for.
Whatever GI pressure specs you find is Apples & Oranges when compared to commercial ammo pressure.

rc

happygeek
December 6, 2009, 03:56 PM
The only 5.56x45mm rifle I own is a Sig 556 and it says 5.56 NATO right on the side of the thing :)

Come to think of it, didn't the Seals crack the slides on some of the early test M9s by firing +P 9mm ammo?

Quick lookup on Wikipedia

Prior to its widespread adoption by the U.S. military, questions were raised in a General Accounting Office report after an incident where a slide failure on a Beretta 92SB injured a Naval Special Warfare member[3] and two more failures were later observed in additional testing. These failures included both military and civilian Beretta models with very high round counts and after investigation they were deemed the result of ammunition supplied by the U.S. Army which exceeded the recommended pressures specified by NATO and by Beretta, but nonetheless provoked a modification in the M9 design to prevent slide failure from causing injuries.

rcmodel
December 6, 2009, 04:05 PM
The ammo that was cracking slides was over-pressure & out of NATO spec to start with.

Following the slide cracking incidents, a change was made to a different power among other things.

rc

happygeek
December 6, 2009, 04:39 PM
Ahhh, good to know. I know the 92FS model has that, ummm, thing that stops the slide from flying off the back at you if it does crack.

kenkel98
July 9, 2011, 11:12 PM
Ok guys,

I don't mean to beat a dead horse about this but...

I have a Ruger Mini-14 Ranch built in 1999. It is labeled .223 on the receiver. I haven't taken it apart to see if the barrel is stamped 5.56, but according to the manual, it will shoot both the .223 and the 5.56.

I have a Colt AR-15 SP1 built around 1973 and it is stamped .223 on the lower. Nothing stamped on the barrel, not even the twist rate.

I have been shooting both .223 and 5.56 ammo in the Ruger for the last 15 years or so. Of course, I really don't shoot it that often. It has probably had less than 1000 rounds put through it but still, no problems with the 5.56 ammo. That's not to say it won't happen, but...

The AR has had quite a few more than that run through it. Both 5.56 and .223. I have always used 55 gr. ammo assuming the twist rate is probably 12.1. Again, never had a problem. Again, not to say it won't happen, but...

I have not seen any difference in accuracy, keeping in mind I have not locked these guns into vices and shot them at 500 yards. I normally shoot between 75 and 150 yards.

I have been a gun "nut" for over 35 years and consider myself very knowledgable. But, I have learned a lot here tonight. I worked part time in a gun store for years, mostly just for the fun of it, but I never knew about the differences between the .223 and the 5.56 rounds. I had always been told that the 5.56 was the military or NATO designation for the .223 and that they were the same round. And I was in the Air Force!! Of course, I only had to shoot the M-16 twice during my 4 years.

I plan to reload the .223/5.56 and have all the dies, powder and bullets to do so.

Everytime I login to this web site I learn something new.

Just my 2 cents worth..

Thanks again THR for being here for us.

K

ugaarguy
July 9, 2011, 11:34 PM
but according to the manual, it will shoot both the .223 and the 5.56. There's the answer on your Mini-14.
I have a Colt AR-15 SP1 built around 1973 and it is stamped .223 on the lower. Nothing stamped on the barrel, not even the twist rate.
It's probably a 5.56 chambered bbl, being an older Colt, but that's a bit before my time. I owned an SP-1 of 1986 vintage (IIRC that's when the Marine who sold it to me told me he bought it new) which was stamped .223 on the lower, but had the standard C MP 5.56 1:12 stamped on the bbl forward of the FSB. Have you taken off the handguards to see if the barrel is stamped underneath them?

isc
July 10, 2011, 12:10 AM
This is the most overblown "controversy" in the gun world and amounts to little more than two old ladies arguing over whether a dress is black or Navy blue.

It doesn't matter. .223 Remington and 5.56x45 are interchangeable designations for the same round and one can't measure the difference between cartidges loaded to the respective specifications doesn't exist.

Using highly sensitive and precise tools one could likely measure the minute variations in chambers, but you can't measure the difference in the cartridges themselves.

ugaarguy
July 10, 2011, 12:30 AM
It doesn't matter. .223 Remington and 5.56x45 are interchangeable designations for the same round and one can't measure the difference between cartidges loaded to the respective specifications doesn't exist.

Using highly sensitive and precise tools one could likely measure the minute variations in chambers, but you can't measure the difference in the cartridges themselves.
The chambers, throats, and leade angles DO matter. Running true 5.56 spec ammo in a .223 chamber that's on the tight side of the SAAMI spec. WILL cause problems. Yes, I've seen it.

M1key
July 10, 2011, 02:08 PM
Colt SP1s were 556 Nato chambered. Owned three, with the first one back in the mid-70's. All shot LC mil surp 5.56.

I guess gun makers are still stamping whatever they want on barrels and receivers, further adding to the confusion.

As posted earlier, even Saigas have ".223 Rem" stamped on their receivers and magazines. The manual lists the cartridge as ".223 Rem (5.56x45)".

M

DJnRF
July 21, 2014, 12:42 PM
This post may be archived, but this is relative, and explanatory.

" The two major changes between .223 Rem and 5.56 NATO are that the throat length is longer and the chamber pressure is measured differently.

“Throat length” is defined as the distance between the end of the cartridge neck and the point at which the rifling in the barrel engages the bullet. In the above image the throat length is clearly identified as the green markings on the bullet and marked as (a) on the barrel.

A longer throat length will allow you to load a heavier bullet (since length is the only way to increase weight with a fixed diameter projectile and using the same materials), which are more accurate at long distances and such. But with lighter bullets, a longer throat means that the bullet will not engage the rifling as quickly as desired and may lead to concentricity errors as the bullet wobbles off center before hitting the rifling. That’s a bad thing, and negatively impacts accuracy.

A shorter throat length means lighter bullets are more accurate. But if you try to load a longer bullet, the short throat length will push the bullet further into the case which increases chamber pressure and can lead to explosions and other bad things.

So, in short, longer is better. And 5.56 NATO is longer."

This is an excerpt on this issue from:
http://www.thetruthaboutguns.com/2013/02/foghorn/ask-foghorn-whats-the-difference-between-5-56-and-223/

The whole point being that if you have a 5.56 chambered barrel, you
are safe to use the .223, But, ..... NOT the other way around!

Dave.

CornCod
July 22, 2014, 11:50 PM
I only rarely use 5.56 in my Colt AR15A2. I use mostly cheapo .223 Russian steel-cased stuff. For me, its largely a question of economics.

DJnRF
July 23, 2014, 06:37 AM
I only rarely use 5.56 in my Colt AR15A2. I use mostly cheapo .223 Russian steel-cased stuff. For me, its largely a question of economics.
Without looking I am not sure if your rifle is chambered for
the 5.56 or the .223.

If your rifle is chambered for the 5.56 you are ok to fire the
.223. If not, you are exceeding the chamber pressure of your
rifle to fire the 5.56 ammo as the longer case length of the
5.56 causes the bullet to be pushed further into the case,
which increases the pressure in the chamber when fired. This
will cause undue metal stress that can cause serious harm
to the rifle at some point. I would suggest you check on the
specifications of the chamber of your barrel.

The attached image shows the difference between the .223,
and the 5.56 rounds. If your chamber is for the .223 the
longer case length of the 5.56 round causes the bullet to
be pushed into the case. Just as automatic pistols chamber
the rounds on the basis of the case length, the chamber of
the rifle is made only long enough for the ammo it is
designed for so that the bullet is properly at the bore with
the rifling. You can see in the image that this rifle is with
the chamber for the 5.56, and that the bullet of a .223
would not quite be fully into the bore of the rifle.


Dave.

sauer1911
July 23, 2014, 11:22 AM
i shoot .223 outta my M&P15 OR 5.56. :)

With iron sights I can hit steel at 450yds. :what:

Seems pretty accurate to me.;)

btw, I rarely see 5.56 ammo around.

be safe

benzy2
July 23, 2014, 02:00 PM
While the original post was 5 years ago I'll add one quick comment.

Cast your chamber if you have doubts. That will tell you what is safe and isn't. I don't believe a single mass produced .223 rifle today is being shipped with a true .223 chamber. Some specialty target rifles/barrels maybe, but I have yet to hear a case where a .223 marked chamber was throated to original .223 spec. With big long heavy bullets and fast twists being popular today, everyone is throating long. It gets you around pressure issues when using 5.56 brass/loads and it gets you around guys jamming the ultra long loads way into the rifling. If you can't load to the rifling while fitting in a magazine, I don't see how a 5.56 or a .223 marked chamber matters nor where shooting either in that chamber would be an issue.

The issue with pressure is a bit overstated. What I find funny is that people claim a 5.56 is loaded hotter than .223 and a .223 barrel can't handle the extra press. Maybe, but both are coming from blanks of the same quality steel of the same size and weight. It isn't like we have .223 barrels that are safe at 55,000psi but can't handle being run at the 60,000psi that a 5.56 makes (assuming those earlier numbers are accurate). The problem is if a 60,000psi load is jammed to the lands raising pressure from there. So the simple answer is long throat the gun, which everyone I have seen is doing just that.

Pressure is a complicated game and it's very difficult to address all variables in a quick post. Many of the considerations are over my head. That said, a quick casting of the chamber or using an OAL gauge will tell you if your potential loads will be in the rifling (and potentially dangerous) or not. I know the chambers on all of my .223 or 5.56 marked barrels are throated far enough out that any commercially available 5.56 ammo I've found isn't a problem and doesn't show signs of dangerous pressure. I can't comment for your rifles nor advise you to use the wrong round/pressure range for the capability of your individual rifle. Figure out what you have and run ammo that is safe.

Ridgerunner665
July 23, 2014, 02:27 PM
5.56 pressure is measured with a transducer at the case mouth...very late in the firing event...actual peak pressure is very likely near the limits of the strength of the brass (70,000 psi)...5.56 is essentially, a 223 loaded to magnum pressure...combine that with a jammed bullet in a short (SAAMI) chamber, and it's not unreasonable to expect pressures that may well "spontaneously disassemble" even a modern bolt action.

Think about it...5.56 is rated at 60,000 psi, but that pressure is measured after the bullet has moved...sort of the same principle as the Weatherby chambers....anybody wanna try firing a Weatherby round loaded to the hilt in a short chamber?

Reloadron
July 23, 2014, 02:48 PM
I bought my 5.56 because of the versatility of being able to shoot both types of rounds in a pinch, and was wondering if anyone else is shooting .223 in their 5.56 rifle? I know that it is not as accurate as a shooting these rounds out of a designated .223 rifle, but how much of a difference is there? I have the opportunnity to get 1000 rounds of .223 for a real good price, but if it is a big difference then maybe it is not worth it.
You don't mention what your rifle is or more specific what the twist rate is?
You also don't mention the bullet weights of these 1,000 rounds of 223 or the bullet design?

So while once again we can beat the 5.56/223 debate to death I really see no way to answer your question beyond saying yeah, you can shoot 223 all day long and all night long in a rifle having a chamber cut for 5.56 NATO.

Ron

benzy2
July 23, 2014, 02:50 PM
Where does the extra pressure come from?

Federal's 62gr .223 Remington load pushes that bullet 3020fps. It's marked .223 Remington. Lake City's 62gr 5.56 NATO 62gr XM855 load is published as 3020fps. It is marked 5.56 NATO. Would we consider Lake City 5.56 marked ammo to be a true 5.56 load or is it loaded light? There is minimal velocity difference between factory .223 ammo and factory 5.56 ammo, certainly hard to believe a 15,000psi difference is present from nearly identical cases shooting to nearly identical velocities. There is more to pressure than velocity, but in two similar cases firing the same bullet, it makes it hard to see why the NATO spec would call for a significant rise in pressure without also benefiting from a significant rise in muzzle velocity.

DJnRF
July 24, 2014, 01:25 AM
Books on the ballistics of ammo do not cover the
problem with pressure when shooting a 5.56 in a
barrel chambered specifically for the .223.

What happens when shooting a 5.56 in a .223
barrel, the throat is not long enough to properly
accommodate the extra length of the 5.56 from
that of the .223. The bullet of that 5.56 round is
jammed farther into the case. Since this reduces
the amount of space for the powder in the case
the pressure is also increased when fired.

The 5.56 Nato round was developed with a higher
pressure at detonation. This pressure, being more
than that of the current .223 round gets much less
space in the case, which increases the pressure
above that of the .223. with ignition of the powder.
Depending upon how far the bullet was pushed
into the case, the resulting pressure can exceed
the technical design of the .223 barrel.

There is no way of knowing how often this can
be done before the barrel literally explodes. Just
insure that you have a 5:56 barrel when shooting
the 5.56 ammo.

Dave.

X-Rap
July 24, 2014, 01:37 AM
I've yet to see a barrel of a 223 "literally explode".
Considering most 223 chambers are of a more robust bolt style it's difficult to imagine they can't withstand the pressures of an auto.
Been pages wasted on this discussion.

Ridgerunner665
July 24, 2014, 05:01 PM
Where does the extra pressure come from?

Federal's 62gr .223 Remington load pushes that bullet 3020fps. It's marked .223 Remington. Lake City's 62gr 5.56 NATO 62gr XM855 load is published as 3020fps. It is marked 5.56 NATO. Would we consider Lake City 5.56 marked ammo to be a true 5.56 load or is it loaded light? There is minimal velocity difference between factory .223 ammo and factory 5.56 ammo, certainly hard to believe a 15,000psi difference is present from nearly identical cases shooting to nearly identical velocities. There is more to pressure than velocity, but in two similar cases firing the same bullet, it makes it hard to see why the NATO spec would call for a significant rise in pressure without also benefiting from a significant rise in muzzle velocity.
M855 will hit nearly 3,000 fps from a 16 barrel...

The Federal load you mention was most likely chrono'd from a 24" barrel...

Also, Uncle Sam places his chrono at 75 feet (IIRC)....Federal probably placed theirs at the traditional 10-12 feet.

DJnRF
July 25, 2014, 02:23 AM
I've yet to see a barrel of a 223 "literally explode"


Now you have seen one!

X-Rap
July 25, 2014, 01:40 PM
And this is the sole result of Nato ammo in a 223 chamber?
There are many photos a destroyed firearms on the net, I guess, given the amount of violation I have committed regarding this issue I would be skeptical if it were to have happened to me personally.
Your example and the catastrophic results would indicate a much greater cause than that of the difference it the factory loads being discussed IMHO.

benzy2
July 25, 2014, 02:03 PM
I'll ask this again, has anyone seen a non-custom chambered .223 marked barrel made in the last 2 decades that actually was tighter than a 5.56 spec at the throat? Has anyone cast a mold of their chambers to know how their rifles were actually cut? I haven't cast them all, but what I have seen is they all come back longer than minimum SAAMI spec. Only you can find out how your chamber was cut. If yours is cut to the minimum spec and you run 5.56 ammo in it, you may have a problem. If it's cut like the rifles I've seen, it won't make a bit of difference. Check for yourself or shoot what you like. I have confidence that nothing I own would have a problem either way.

HoosierQ
July 25, 2014, 02:17 PM
Makes me glad my rifle is clearly marked 5.56! Every once in a while, I get lucky:)

Robert101
July 25, 2014, 02:54 PM
All of the above considered, what happens when you then reload that .223 or NATO round and stick it in the chamber? This is a reloading section so how do you guys address reloading each type of that brass?

I address this the same way with 308 Winchester and 7.62X51 NATO. Once reloaded (and there are no 7.62X51 dies) it is simply a matter of SAMMI specifications or match for your barrel.

HOOfan_1
July 25, 2014, 03:24 PM
the dimensions of the brass are exactly the same.

barnbwt
July 25, 2014, 08:52 PM
Makes me glad my rifle is clearly marked 5.56!
The marking isn't what you should be interested in. My R51 is "marked" 9mm Luger, and yet a Luger finishing reamer only dropped halfway in when I went to clean up Big Rem's hack-job. Not saying whatever your gun is is a hack job, but it's what's inside that counts. Trust, but verify.

Personally, I think the whole "NATO Chamber" stuff is the exact same phenomena we've seen since forever in military guns; they have generous chambers so brass/gun fit is less of an issue. Makes things easier, cheaper, and more reliable all around (by which I mean, shooter, armorer, ammo sourcer, ammo manufacturer, and countless inspectors)

Unless you're see rifling grooves engraving or unfired cartridges having trouble chambering under their own weight, it's pretty much impossible for the variances described between the chambers to have much impact on anything. Yes, if innumerable factors line up to conspire against you, the civilian chamber spec could be the straw that breaks the camel. But so could be the fact your NATO Milspec Tacktical chamber was the last one cut before the reamer was thrown in the trash, and made it through with a narrow, rough, chattered, or uneven chamber.

Many guns, like the K31, were designed to have essentially zero freebore, with the rifling grooves contacting the ogive when chambered. No sign of those situations being particularly crazy, as far as pressure (though it obviously is a bit higher). The force required to start a bullet down a bore is like 100lbs; the bolt thrust on your rifles is like 60 times that. And in any case, bolt thrust is what actually matters, and less so what the bullet is doing.

It's worth remembering your AR barrel extension is an incredibly strong mechanical and geometric marvel that has a very healthy design safety margin. Stuff that bumps the design load 10% one way or the other (like a slightly higher pressure load or a hot day) will not have any bearing on practical safety. At worse, it may accelerate wear somewhat (oh noes, 18000 instead of 20000 cycles between mean failures :rolleyes:). Any gun so sensitive was never safe to fire in the first place (which some could argue certain low end parts may be. I'd be more worried they set my headspace wrong or forgot to heat-treat, than if they cut the wrong type of chamber in such a case, though)

TCB

DJnRF
July 26, 2014, 03:18 AM
the dimensions of the brass are exactly the same.

The 5.56 mm NATO and .223 Remington cartridges and chamberings are similar but not identical. While the cartridges are identical other than powder load, the chamber leade, i.e. the area where the rifling begins, is cut to a sharper angle on some .223 commercial chambers. Because of this, a cartridge loaded to generate 5.56mm pressures in a 5.56mm chamber may develop pressures that exceed SAAMI limits when fired from a short-leade .223 Remington chamber.
The result of this is that there is no such thing as "5.56 brass" or ".223 brass", the differences in the cartridges lie in pressure ratings and in chamber leade length, not in the shape or thickness of the brass.

Pressures are generated and measured using a chamber cut to 5.56 NATO specifications, including the longer leade. Firing 5.56mm NATO from a chamber with a shorter .223 Remington leade can generate pressures in excess of SAAMI maximums.

To always be sure your rifle is able to handle these extra pressures you must check your chamber. If your rifle barrel is marked as for 5.56mm NATO, you most likely have no problem on this issue. If it is stamped as for .223 ammunition, make a mold of your chamber and measure it to be sure.

ugaarguy
July 26, 2014, 04:15 AM
the dimensions of the brass are exactly the same.
The external dimension are, but the internal dimensions are not. True 5.56 brass is thicker, and every reloading manual will tell you to reduce .223 Rem loads when using military 5.56 brass to avoid exceeding max pressure.

External dimensions aside, the chamber dimensions differ significantly enough that firing full pressure 5.56 NATO loads in .223 REM chamber can be problematic.

HOOfan_1
July 26, 2014, 12:07 PM
I think brass thickness varies just as much by who manufactures it moreso than whether it is stamped .223 or 5.56x45.

http://www.thehighroad.org/showthread.php?t=606455

Easiest thing to do is just work up your load from the minimum like you should do with any cartridge.

benzy2
July 26, 2014, 01:18 PM
This debate is theoretical and meaningless. Who is cutting a tight .223 Rem chamber and installing it today on a commercially available rifle? Not just mark the gun but who actually is running minimum throat spec and stamping it .223? You could call it 22lr for all I care. It's how the thing is cut that matters and nobody with lawyers on staff are letting 223 marked rifles go out the door with chambers that aren't safe with 5.56. They may suggest against it, but their lawyers aren't dumb and theydo get their way.

X-Rap
July 26, 2014, 01:37 PM
pressures in excess of SAAMI maximums.[/B]
]

Are these pressures really high enough to cause chamber failure? What pecentages are we talking about.

This issue is rehashed often and the same tribal knowledge is always repeated.
There is some CYA on the part of gun makers but not to the extent that they roll a warning on their barrels. I've never seen a warning on Nato spec ammunition like you find on ammo that fire in both black powder and smokeless guns.
To each their own, if you have Nato spec ammo and 223 rifle send me all you have, my guns don't seem to know the difference.



The external dimension are, but the internal dimensions are not. True 5.56 brass is thicker, and every reloading manual will tell you to reduce .223 Rem loads when using military 5.56 brass to avoid exceeding max pressure.

External dimensions aside, the chamber dimensions differ significantly enough that firing full pressure 5.56 NATO loads in .223 REM chamber can be problematic.

Welding Rod
July 26, 2014, 02:48 PM
First hand experience....

My 20 inch 556 BCM uppers periodically short stroke on some 223 ammo. Same ammo works fine 100% of the time in my Wylde chambered Rock River 20 inch uppers. I am not saying this is due to chamber dimensions, could be gas port size, but none-the-less the ammo makes a difference. All of the uppers work fine with 556 ammo.

My Mini 14 suffers frequent failures to fire / light firing pin hits with 556 ammo, presumably due to beefier primer cups.

Likewise my 308 M&P 10 works fine on 308 ammo and short strokes with some 7.62 ammo.

X-Rap
July 26, 2014, 03:12 PM
I have an AR that consistently failed to go into battery with all ammo I tried, a trip to the smith and his reamer fixed it to 100% reliability since. It is marked 556.
I suppose that there are many chambers that barely fall within spec due to their position in manufacturing and new or worn tooling. Some no doubt slip by as being out of spec.

DJnRF
July 27, 2014, 02:06 AM
When excessive pressures have happened they were not being measured
for the most part. Tests done after the fact have shown some pressures
to have attained over 71,000 pounds. Since the proper pressure for the
.223 is around the 49,000 pound range, and the 5.56 is around the
52,000 pound range, those pressures up around 71,000 pounds for a
5.56 fired in a .223 chamber can cause serious damage, and possible
injury.

This is not a game, nor an issue to bandy about. Heed the warnings
and just be sure of what you are using. If you wish to become a
ballistics expert, study it and do your own builds from scratch, and
test the weapons. You would need to become an engineer for the
math needed for your testings as well as knowing how to determine
the ballistics for and from any specs. Otherwise, just consider the
warnings as possible and use due caution.

Just remember that there is always a 50/50 chance that anything
can happen. That is not a degree of probability, just possibility.

barnbwt
July 27, 2014, 01:30 PM
The external dimension are, but the internal dimensions are not. True 5.56 brass is thicker, and every reloading manual will tell you to reduce .223 Rem loads when using military 5.56 brass to avoid exceeding max pressure.
I've heard the same claim with regards to 308 vs. 7.62x51, when we all know they are exactly the same thing, with the NATO round being short-hand for a specific set of pre-approved loads that fall within the 308 standard.

Fun fact; the web article that came up with the super-scary 71ksi figure and all the theories for why this matters so much, just happened to be selling a service to bring '223' chambers into compliance with NATO standards. The psi measurement used for standardization is just that; an arbitrary standard, whose measurement technique and consistency is far more important than exactly how high pressure might actually reach, measured other ways. The whole point of SAAMI is that, a certain cartridge/chamber combination, which when fired to reach a certain pressure measured a certain way, will function safely. Not saying they're full of it, but rather that the whole issue is more overblown than it deserves, precisely because 'non-engineers' would rather pay for a different combination of numbers to be stamped on the outside than understand what is happening. Any number of gun products operate on the same principle of playing off the fears of the ignorant (lubes are probably the worst offenders :D)

A tight chamber raises pressures; doubtless. A tight chamber can happen with any spec, and does happen with every mass-produced chambering. Same thing for oversize brass (do you mic every round you shoot to make sure the shoulders were placed properly? After all, we're all so paranoid about headspace; how much variance do you think manufacturers here and beyond have lot to lot, maker to maker? If a .003" headspace variance is life-critical, wouldn't the same hold for the brass?). I also wonder how many folks have bothered to slug their barrels, let alone do chamber castings; chrome lining variances could easily make the bore tighter than necessary, causing pressure spikes in guns used exclusively with jacketed ammo.

In summary, lots of things can go wrong, and the numbers "5.56" don't actually change that. I will second calls for evidence to be brought out showing that "223" stamped chambers sold commercially have consistently short leades and tight throats to a degree that would impact anything other than accuracy (the term is a "match chamber" when a tight chamber is a 'feature'). Everyone involved in gunnery knows the rounds are so similar that people can and do shoot them interchangeably; why would you not verify a commercially sold rifle was safe to do this in (even if you won't endorse the practice)? Can someone mic some 223/5.56 rounds from the same manufacturer and see if they're even using different tooling besides the headstamp die? If not, that would lead me to draw some conclusions about what barrel makers are likely doing...

If rounds are not engraving on lands, or wedging into the action, how could "tightness" possibly be affecting anything? Does a few thou of lacquer buildup at the neck cause a kaboom? Not in any significant number. Are your 5.56 cases losing all their primers to cratering, pierces, or loose pockets when fired from a 223? If not, what are those supposed scary pressures doing?

TCB

DJnRF
July 28, 2014, 12:28 PM
I've heard the same claim with regards to 308 vs. 7.62x51, when we all know they are exactly the same thing, with the NATO round being short-hand for a specific set of pre-approved loads that fall within the 308 standard.

Fun fact; the web article that came up with the super-scary 71ksi figure and all the theories for why this matters so much, just happened to be selling a service to bring '223' chambers into compliance with NATO standards.

The mention of claims about the .308 vs 7.62 are exactly opposite of the
ballistic testing of the .223 vs the 5.56. The difference between the .308 and
the 7.62 are reversed from that of the .223 and 5.56 ammunition.

In the case of the 7.62 it actually calls for a smaller chamber size leade than
the .308. It is perfectly alright to fire 7.62 in a .308 rifle. Even the chamber
pressure of the 7.62 is lower than that of the typical factory round of the .308.
For the 7.62 the standard chamber pressure was held at the typical 50,000
pounds just as was the 30-6 ammunition fired in the M-1 rifle and 30 cal.
machine guns. Even the civilian 30-06 ammunition were exactly the same
overall dimensions as the military, even though the pressures were, at times,
more.

I have a .303 Enfield Mk 1. The problem exists with the .303 that five
different rounds were made for the .303 by the British. I have to 'slug'
my chamber to insure it is safe to fire with any .303 ammunition. When
I reload I can then insure I have the right ammo. Otherwise, I could have
a problem if I do not check my rifle first. The fact that I got this rifle many
years back, and that it only was fired with the ammo that had come with
it doesn't give me any information to be sure of anything.

As for the mention of a web site of a company that wanted to sell "a service to bring '223' chambers into compliance with NATO standards." I am totally
unaware of that article. In fact, my information came from a report by the
U.S. Army Ballistic Research Laboratory, Vulnerability/Lethality Division.
Recently, I also read an article on this in The Firearm Blog. My first info on
this was about a year back from the Army Lab.

One thing I have also heard, but since retired have not contacted any of
the manufacturers to confirm, is that many (possibly most) have started
making their .223 rifle chambers to the specs required for the firing of the
5.56 ammunition. In years past when I was in this business I would have
contacted all of the manufacturers of barrels for the .223 to verify this
information. Each of you skeptics, naysayers, and anyone else who would
like to insure their rifle is made with a chamber to fire the 5.56 ammo
safely should also contact the maker of your rifle barrel. I would never let
myself be so ignorant to not insure I have a rifle safe to fire any ammo
claimed to be 'the same'.

In my case here I only have one rifle that fires the same caliber. I am
certain that it has the military barrel as it was one made just for that
purpose. However, any of you that has a .223 rifle that was not specifically
made for the military NATO specs should contact your barrel maker to be
sure of what you have. Don't let yourself be so much of a nincompoop that
you would rather just continue on in a forum to hear yourself make dumb
claims about anything that can involve your own safety, and the safety of
others.

I have stated only facts in here without insisting anything specific about
any particular rifle, or manufacturer. Just facts of the reports, and facts
cannot be changed. Instead, they must be verified. In the particular case
of any claim made about a specific part (such as the barrel in this case),
it behooves each individual to verify the matter for their own safety and
protection from possible harm. Never take the word of a 'nincompoop' that
isn't in the business of making and testing their parts as this is no more
than rumor and hearsay. You take that kind of info just with a 'grain of salt'.
If you put all of the opinions and hearsay into a paper sack it is worth exactly
the price of the paper sack. Verify for your particular need!

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