.223 cal vs. 5.56mm


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leadcounsel
November 29, 2011, 01:54 AM
This has been talked to death...

But as a refresher can .223 be used in a 5.56 rifle or vise versa

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RhinoDefense
November 29, 2011, 01:55 AM
5.56 is for 5.56 and may be used for .223.

223 is 223 only.

Ar180shooter
November 29, 2011, 02:04 AM
5.56 is for 5.56 and may be used for .223.

223 is 223 only.
Lots of people have shot 5.56 out of their .223 marked AR's over the years without any ill effects.

RhinoDefense
November 29, 2011, 02:08 AM
Good for them.

Not every AR marked ".223" actually has a .223 chamber. Some chamber 5.56 but mark .223. You can take the chance, I won't.

Ar180shooter
November 29, 2011, 02:21 AM
I don't base what I say on nothing.

December 4, 2002

TECHNICAL NOTE 45: 5.56 NATO vs SAAMI .223 REMINGTON CHAMBERS

BACKGROUND: We are often asked whether our rifles feature NATO (North Atlantic Treaty Organization) or SAAMI (Small Arms and Ammunition Manufacturers Institute) standard chambers, and whether it makes any difference.

FACTS:

.223 Remington (SAAMI standard) and 5.56mm (NATO standard) rifle chambers are almost identical. The difference is largely limited to the “freebore,” the cylindrical space in front of the case mouth, and the “lead” or “leade,” the the tapered region that eases the bullet into full engagement with the rifling. NATO and SAAMI cartridges can normally be used interchangeably with no problem.

The SAAMI chamber features less freebore and a tighter leade, which normally provide better bullet fit and match-grade accuracy than the NATO chamber. It is wonderfully suited to match bullets.

Millions of rounds of NATO ammunition have been fired safely in Eagle Arms' and ArmaLite’s SAAMI chambers over the past 15 years. Occasionally a non-standard round (of generally imported) ammunition will fit too tightly in the leade, and resistance to early bullet movement can cause elevated chamber pressures. These pressures are revealed by overly flattened or powder stains that reveal gasses leaking around the primer.

The first few rounds of ALL ammunition, from whatever source or lot, should be checked for pressure and other signs of defect before firing large quantities. If you have a problem, you can generally bet that the ammunition meets neither SAAMI nor NATO specifications.

ArmaLite has adopted a practice of using a special, modified SAAMI chambers in its stainless steel match barrels. This chamber is better for match use than the NATO chamber, but fires the NATO ammunition perfectly. We use the NATO chamber in all moly (phosphated) and chrome-lined barrels.

ArmaLite’s larger AR-10® rifles are all chambered with 7.62mm NATO chambers. .308 Winchester (SAAMI standard) ammunition functions perfectly in the 7.62mm chambers.



© 2001 ArmaLite, Inc®.Basically, if the ammunition and your chamber are within their respective specifications, there should be no interchangeability issues. Also, it wouldn't surprise me if you were to examine several samples of .223 and 5.56 chambers, you would find that there was more variance between samples from the same set of specifications than between sets, due to manufacturing processes and accepted tolerances.

allaroundhunter
November 29, 2011, 03:02 AM
I will shoot .223 Rem out of a chamber marked 5.56 NATO, but not vice versa.

LoonWulf
November 29, 2011, 04:52 AM
I've got to admit I fired a lot of surplus ammo out of my .223 Remington 700. I never had any issues at all but that's one person and one gun.

K-Rod
November 29, 2011, 05:30 AM
Been down this road a few times but I'll travel it again. You can shoot .223 through your 5.56 but your accuracy is gonna suffer it. DO NOT SHOOT 5.56 IN YOUR .223!!! 5.56 is a NATO round designed for military specs. Its loaded at a much high pressure than .223 & though it may or may not KA-BOOM your rifle, it very likely will damage it.

I shoot .223 through my 5.56 chambered AR. Never had any issues. I won't shoot 5.56 in my .223 bolt guns though. Why chance it? When or if in doubt, just run what the weapon chambered for.

buttrap
November 29, 2011, 06:13 AM
Good share of .223 guns are made to shoot 5.56 and have a 5.56 chamber. I would not worry about it unless is a match chamber .223.

bigedp51
November 29, 2011, 06:15 AM
leadcounsel

If you want mass confusion in an open forum ask about the .308/7.62 NATO or the .223/5.56. If you do your research and sift through the garbage while studying the subject looking for "FACTUAL" information you will find the following:

1. CIP the European equivalent of the American SAAMI considers the .308/7.62 and the .223/5.56 the "SAME" cartridge.

2. Military chamber pressure readings are taken at the neck of the cartridge and American SAAMI chamber pressure readings are taken at the mid point of the cartridge body. Military pressures read higher than SAAMI pressure readings "BUT" they are one in the same actual chamber pressure. (example, 60 mph = 100 kph and both are the same actual speed)

3. The only difference between the two rounds is the M16/A4 "now" has a longer throat to accept the heavier and longer military bullets. The older and some of the newer .223 have a "shorter" throat and slower twist rate of 1 in 14 twist. My new .223 has a longer throat with a 1 in 9 twist and the manual states it can safely shoot either type ammunition. If you shoot the newer 5.56 military ammunition in rifles with a 1 in 14/1 in 12 twist the shorter throat will cause pressure spikes when shooting the "longer" and "heavier" military bullets. (pressure spikes, chamber pressures that are higher and peak sooner than normal)

Below, .223 and 5.56 throat differences
(short throat = light shorter bullets, long throat = heavy longer bullets)

http://i122.photobucket.com/albums/o254/bigedp51/556natochamberversus223remingtonchamber02.jpg

Below, eight variations in .223/5.56 camber types and throating for the "SAME" cartridge.

http://i122.photobucket.com/albums/o254/bigedp51/223reamers-1.jpg

The .223 cartridge and the 5.56 cartridge for a practical purposes are the same, the difference is "some" .223 rifles were designed were to shoot shorter and lighter bullets and the "military" keeps changing bullet types to get the M16 to hit harder and have more knock down power.

NOTE: Before I bought my heavy barrel .223 Stevens 200 I knew it had a longer throat and a 1 in 9 twist and I would be able to shoot both types of ammo without ANY problem.

Below, two of my "civilian" :rolleyes: rifles that can shoot "military" ammunition, .223 Stevens 200 and a Remington 700 30-06.(and I still have both my eyes and all my fingers and both rifles are in one piece) :eek:

http://i122.photobucket.com/albums/o254/bigedp51/IMGP7358.jpg

Five gallon buckets of .223 and 5.56 cartridge cases waiting to be reloaded next to my reloading bench. ;)

http://i122.photobucket.com/albums/o254/bigedp51/IMGP6526.jpg

buttrap
November 29, 2011, 06:26 AM
Another neat deal is 5.56 and .223 brass pretty much weight the same too so you dont have to worry about cutting back loads like you do with GI .30 cal brass vs commerical brass.

303tom
November 29, 2011, 11:12 AM
They are the same. Call Lake City & ask them here is there number.

1-816-796-7156

Bartholomew Roberts
November 29, 2011, 11:18 AM
And to add to the confusion, many chambers marked .223 aren't cut to .223 SAAMI specs; just as many chambers marked 5.56mm aren't cut to 5.56mm NATO specs. Many manufacturers use a hybrid chamber knowing that their customers may be shooting a wide variety of ammo but will still expect high levels of accuracy.

If you get something like a Michiguns 5.56 gauge and start actually measuring random AR chambers, you'll be shocked at how few are actually cut as 5.56 chambers, markings or not.

Having said that, the worst I've seen happen by firing 5.56 NATO ammo in a short-leade .223-ish chamber is that the gun will pop primers/fail to cycle properly. No kabooms, parts breakage or anything dramatic.

ApacheCoTodd
November 29, 2011, 01:05 PM
Generally, the only issues you're likely to run into are well stated in the Armalite quote above. If you're concerned regarding your ammo - at the range - allow a full round to be seated without assistance (rifle action only) into the chamber and extract it to view the areas of the ogive for signs of contact with the lands of the rifling. To be a little more particular, dip the projectile in layout fluid or simply black it with a sharpie.

RhinoDefense
November 29, 2011, 01:08 PM
Bigedp51, the brass for .223 and 5.56 are the same. .223 and 5.56 are chamber nomenclature and specifications, not brass. 5.56 NATO ammunition is also loaded with a pressure measurement taken at the case mouth whereas SAAMI .223 is taken at the chamber. Two very different measurements and they are not interchangeable.

bigedp51
November 29, 2011, 01:49 PM
RhinoDefense

1. I said NOTHING about brass.

2. If the SAAMI measures chamber pressure for a military cartridge and gets "X" for a pressure reading and the military measures pressure using EPVAT method for the same cartridge and gets "Y" for a reading, then "X" and "Y" equal the same pressure. And I did NOT say the EPVAT and SAAMI pressure taking measurements were the same, do NOT put words in my mouth and try and read what a person writes more carefully. ;)

Example below, between CUP and PSI pressures for the .308 and 7.62 NATO. (done with a little humor) :rolleyes:

As you can see below it is safe to put 32 PSI in your tires BUT if you put 220 kPa in your tires they will blow up and kill everyone in a 300 yard radius. :eek:


http://i122.photobucket.com/albums/o254/bigedp51/IMGP3024-1.jpg

MrDig
November 29, 2011, 02:12 PM
I think this would make a good Mythbusters topic. along with the 308/7.62 nonsense. Anyone else want to join me in sending the topic to them? It appears you need to join that forum to suggest it, but I think if we make it a hot topic they would pay attention.

RhinoDefense
November 29, 2011, 04:00 PM
Bigedp51, you're just not understanding.

coug
November 29, 2011, 05:15 PM
The 5.56 has a higher pressure rating than the .223 but I have yet to see any difference in shooting 5.56 loads out of the load manuals in a .223, They always list heavy bullets in 5.56 pages and light bullets in .223. I shoot 75 gr A-Max bullets in my Savage .223 and they have shot well for about 6000 rounds.

Ar180shooter
November 29, 2011, 06:45 PM
Bigedp51, the brass for .223 and 5.56 are the same. .223 and 5.56 are chamber nomenclature and specifications, not brass. 5.56 NATO ammunition is also loaded with a pressure measurement taken at the case mouth whereas SAAMI .223 is taken at the chamber. Two very different measurements and they are not interchangeable.
The two pressure readings are different because they are taken from different places. This has no bearing on compatibility. What would concern you is the chamber specifications, which are virtually identical, except for increased freebore in NATO spec chambers, which is to accommodate the heavier bullets used in NATO ammunition.

TxBobS
November 29, 2011, 06:53 PM
Lots of people have shot 5.56 out of their .223 marked AR's over the years without any ill effects.

And NASA flew for years with foam on the tanks without any ill effects.

While the rounds are nearly identical in size, the pressure specs are different.

A 5.56 barrel has to be able to handle 62,366 PSI while a .223 only has to be able to hold max. pressure of 55,000 PSI.

Is that 7k difference going to matter? Most likely not unless there was already some type of defect in the barrel or just a poorly made barrel. But I'm not shooting rounds that can develop more pressure than what the gun was designed for and a .223 was designed for less pressure than a 5.56 can develop.

stchman
November 29, 2011, 07:23 PM
From what I understand there are some very slight differences in .223 and 5.56. My Mini-14 shoots both with 5.56 having a touch more recoil.

I personally think that the AR guys use 5.56 because 5.56 sounds cooler to them .223.

wally
November 29, 2011, 07:49 PM
I'm still waiting for the report of an actual safety issue from shooting 5.56 in .223 chamber or vice-versa.

I'll retire from the referral fee to the lawyer who gets the slam dunk product liability case.

See AR180Shooter's post near the top of this tread. Guess this will never be put to rest.

AABEN
November 29, 2011, 09:04 PM
I have 3 223 and I have shot thousand's of 223 and 5.56 and never had any trouble with them. I also reload for them and had never had any trouble with them. My buddy goes out west to shoot Peria dogs every year and he takes 3 223 and 8000 rounds for them.

Strykervet
November 29, 2011, 09:31 PM
That's ridiculous. Picking a calibre based on how "cool" it sounds.

We tend to use 5.56 because of all the confusion apparent on here --if it is okay to use .223 in 5.56 but not the other way around, and you can't get clarity on the issue, then just go with the safest bet. It would be like if the same argument existed over .357 and .38, why take the chance? Just get a .357 and be done with it. Because our loadings are limited by magazine length, the exotic chamberings and extra leade do little to sway the argument one way or the other for the AR crowd.

Finally, when in doubt, just match the number on the headstamp or box to the number on the barrel and problem solved. This should have been included in your basic firearms knowledge package you got way back when. Use all others at your own risk.

ApacheCoTodd
November 29, 2011, 09:55 PM
So, how 'bout this simple question then; excluding blockages, bad re-loads, flattened primers, poorly dimensioned chambers or any other obvious issue - who knows of a 5.56 round catastrophically failing in a .223 rifle? Or more to the point - a factory manufactured .223 barrel catastrophically failing due to a factory manufactured 5.56mm round?

Not sharpshooting here - I'd really like to know the circumstances beyond "I knew a guy once..."

Redneck with a 40
November 29, 2011, 10:07 PM
My mini-14 is marked 223/.556 on the barrel, so I'm good to go.

ApacheCoTodd
November 29, 2011, 10:45 PM
""My mini-14 is marked 223/.556 on the barrel, so I'm good to go.""

That's interesting - if a corporation as in tune with liability as Ruger does that...

And given that I've seen Mini-14 bolts broken by the old Wolf ammo showing they are not indestructible, Ruger still sees no threat in the mixed designation.

That certainly is worthy of note.

Redneck with a 40
November 29, 2011, 11:18 PM
I stand corrected, just pulled my Mini-14 out and checked it. Its stamped .223 on the reciever, but the owners manual states that .223 or standard U.S military 5.56 ammo can be used. So I'm good either way.

I've already fired more than several boxes of 5.56 Nato ammo out of this thing and nothing bad happened, lol.

LoonWulf
November 29, 2011, 11:35 PM
From what ive read/heard/asked the minis have always had a TRUE 5.56 chamber. They are marked .223 tho. If i load my 68grn hornadys full out in my mini the coal is well over mag length. If i remember its 2.46 or something....ill have to go look i made up 5rnds loaded out to touch the lands (same 26grns of 748) just to see if it would create an issue....it did, printed a group under 1", now i want a longer magazine LOL.

Ar180shooter
November 30, 2011, 01:24 AM
And NASA flew for years with foam on the tanks without any ill effects.

While the rounds are nearly identical in size, the pressure specs are different.

A 5.56 barrel has to be able to handle 62,366 PSI while a .223 only has to be able to hold max. pressure of 55,000 PSI.

Is that 7k difference going to matter? Most likely not unless there was already some type of defect in the barrel or just a poorly made barrel. But I'm not shooting rounds that can develop more pressure than what the gun was designed for and a .223 was designed for less pressure than a 5.56 can develop.
Do you know why those numbers are different?

Well, I'll tell you (as apparently you haven't read the rest of the thread as the answer is contained in it). The pressure is measured in different places on the chamber. That is all, and that explains the difference. The chamber specifications are, for all intents and purposes, the same. If you have two identical chambers, you're not going to have dangerous pressures in one, but safe pressures in the other because the barrels are stamped differently.

TxBobS
November 30, 2011, 01:37 AM
Do you know why those numbers are different?

Well, I'll tell you (as apparently you haven't read the rest of the thread as the answer is contained in it). The pressure is measured in different places on the chamber. That is all, and that explains the difference. The chamber specifications are, for all intents and purposes, the same. If you have two identical chambers, you're not going to have dangerous pressures in one, but safe pressures in the other because the barrels are stamped differently.

Well I thought I did but maybe not. Are you saying that because the chambers are the same size that the pressures will be the same? Powder, case volume and bullet weight have no affect on pressure?

Ar180shooter
November 30, 2011, 02:07 AM
Well I thought I did but maybe not. Are you saying that because the chambers are the same size that the pressures will be the same? Powder, case volume and bullet weight have no affect on pressure?
How will 2 chambers that have identical specifications have different pressures when firing the same ammunition?

303tom
November 30, 2011, 02:09 AM
How will 2 chambers that have identical specifications have different pressures when firing the same ammunition?
Chambers are not the same.......

Ar180shooter
November 30, 2011, 02:18 AM
Chambers are not the same.......
For all intents and purposes they are, and you would find a greater variance in the actual measurements of the chambers of their respective standard in reality than there is on paper (due to manufacturing tolerances and having many different manufacturers, not to mention great variance in the actual ammunition used). As mentioned, a greater amount of freebore is usually provided on NATO chambers, but unless using very heavy bullets, the effect this will have on operating pressure is not a concern.

Really though, at this point I'm just parroting what is contained in the ArmaLite letter I posted earlier...

RhinoDefense
November 30, 2011, 02:23 AM
For all intents and purposes they are
No they are not. Why can't you get that through your head?

A .223 Remington chamber is not a 5.56x45mm NATO chamber. Get it? Apparently not. There's plain English for you. Toss that around a bit until it sinks in.

TxBobS
November 30, 2011, 02:29 AM
How will 2 chambers that have identical specifications have different pressures when firing the same ammunition?

Well the chambers don't produce the pressure, they have to contain it.

Will case volume, powder and bullet weight affect pressure? The answer is yes. So within the same chamber you can have vastly different pressures by changing any of the variables. The question then becomes is possible that a 223 chamber could be designed to handle less than a 5.56 chamber. I'm not willing to risk body parts on saying they all are the same.

bigedp51
November 30, 2011, 06:58 AM
RhinoDefense

Did you ever hear anyone say you shouldn't shoot military 30-06 ammunition in a civilian commercial 30-06 rifle? The military chamber for the 30-06 is different than the commercial civilian 30-06 chamber.

All these "issues" with military cartridges and chambers started when we started using the transducer method of taking chamber pressure readings instead of the older CUP or copper crusher method which gave approximately 10,000 psi difference in pressure readings for the exact same pressure readings. (50,000 cup = 60,000 psi)

On top of this the military standardized the pressure measuring methods with NATO countries with the EPVAT testing system measuring chamber pressure at the neck of the cartridge.

"The 5.56 mm NATO and .223 Remington cartridges and chamberings are similar but not identical. Military 5.56mmx45 cases are often made thicker and therefore have less case capacity.[17] However, the NATO specification allows a higher chamber pressure. NATO EPVAT test barrels made for 5.56 mm NATO measure chamber pressure at the case mouth, as opposed to the location used by the United States civil standards organization SAAMI. The piezoelectric sensors or transducers NATO and SAAMI use to conduct the actual pressure measurements also differ. This difference in measurement method accounts for upwards of 20,000 psi (140 MPa) difference in pressure measurements. This means the NATO EPVAT maximum service pressure of 430 MPa (62,000 psi) for 5.56 mm NATO, is reduced by SAAMI to 55,000 psi (380 MPa) for .223 Remington.[18] In contrast to SAAMI, the other main civil standards organization C.I.P. defines the maximum service and proof test pressures of the .223 Remington cartridge equal to the 5.56 mm NATO."

5.56×45mm NATO
http://en.wikipedia.org/wiki/5.56%C3%9745mm_NATO

NATO EPVAT testing
http://en.wikipedia.org/wiki/NATO_EPVAT_testing

RhinoDefense, military chambers are normally larger in diameter and "longer" in headspace than commercial chambers. Military cartridge cases are made more robustly than their civilian counterparts and they DO NOT have to be thicker and can be made of a higher grade brass and be stronger than their civilian counterparts.

In closing RhinoDefense and everyone else read this, anyone with two fingers and a computer can write anything they want on the internet.................

Its up to the reader to sort through the fecal matter to get to the truth. ;)

Below is some good reading.

5.56mm NATO versus 223 Remington Chamber Differences
http://www.m4carbine.net/showthread.php?t=55149

Attack of the (M193) Clones
http://www.ar15.com/forums/t_3_16/511804_.html

Art Eatman
November 30, 2011, 10:30 AM
Post #5 answered the OP.

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