Aren't 5.56 and .223 the same round?

[usmarine0352_2005]

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This may sound stupid, but I was always under the impression that 5.56 was the military equivalent of .223 and that a .223 round could be fired through a 5.56 rifle and vice versa.




Am I wrong?


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[Boomie]

Not vice versa.

http://en.wikipedia.org/wiki/5.56mm#5.56mm_NATO_versus_.223_Remington

 

[Rob G]

They're very similiar but not quite the same. I don't know enough about the specifics for a full explanation but the short version is, you can shoot a .223 in a gun chambered for 5.56 with no problems. But you should never shoot a 5.56 in a gun chambered for .223.

 

[Guns and more]

Am I wrong?

Yes.
The difference is slight but is due to the "lead" or shape of the bullet.
The bottom line is that you can shoot .223 from a barrel marked .556,
but you can't shoot .556 from a barrel marked .223.
So, if you buy a rifle marked .556, you can shoot either.

 

[jungle]

The real difference is in the chambering. The external dimensions of the cartridges are the same.
Loaded to NATO standards, 5.56 in a chamber with tighter throat specs can cause problems. Some gunmakers have changed their .223 specs to more closely mimic 5.56 chambers to reduce the chances of pressure spikes.

The answer is: it varies by maker, and it is hard to determine without careful measurement. To be on the safe side keep military spec ammo out of non milspec chambers.

There is a lot of "5.56" ammo out there, but most of it is not loaded to NATO pressure specs unless it is actual Nato country surplus.

 

[Z-Michigan]

What jungle said. Read and re-read, that's the complete issue. And the chamber differences are such that while people often talk about a 223 chamber or a 5.56 NATO chamber, many chambers are in-between the exact prints of those options.

 

[rcmodel]

is due to the "lead" or shape of the bullet.

Leade is the correct spelling.
And it doesn't apply to bullets.
The shape of the bullet is determined by the ogive profile.
.223 & 5.56 bullets are all pretty much shaped the same.

The "Leade" is the tapered portion of the bore right in front of the chamber before the rifling begins.
It's purpose is to offer a smooth transition from the case to the rifling in the bore.

It is slightly longer in a 5.56 chamber in order to handle longer for thier weight tracer bullets.

It is shorter in a .223 chamber in order to improve accuracy with varmint type bullets. Since tracers are not loaded in .223, the leade doesn't need to be long enough to handle them.

rc

 

[atchcook]

No and not all 5.56 barrles can use higher grain 5.56

You can use 223 in 556 but not the other way around (I have seen it done with no problem but I wont they may have just been lucky). ALSO incase you get the big grain lead(82 grain I think ) match you have to have a longer throughted 5.56 barrel to use them. (I hope my spelling is ok , I try but not perfect I know) . 1 More thing the wolf steel cased 223 is cheap for just plinking but DO NOT USE IT IN YOUR AUTOMATIC! I have seen the bad jams from this where they need to be removed by a gunsmith. Buy the better ammo it will save some money in the long run.

 

[Big Bad Bob]

I have seen now that more and more AR maker's are starting to offer the .223 Wylde chambering, which does allow for both 5.56 and .223 ammo to be used.


Not to be a gomer, but how many times has this question been asked?

 

[Bartholomew Roberts]

As Z-Michigan already pointed out, jungle gave the A+ answer.

 

[JohnBT]

"A Savage rep" <= salesperson

If they made the gun to shoot 5.56 it should be clearly marked on the barrel. The Savage site lists them as .223.

 

[Guns and more]

Leade is the correct spelling.
And it doesn't apply to bullets.
The shape of the bullet is determined by the ogive profile.
.223 & 5.56 bullets are all pretty much shaped the same.

The "Leade" is the tapered portion of the bore right in front of the chamber before the rifling begins.
It's purpose is to offer a smooth transition from the case to the rifling in the bore.

It is slightly longer in a 5.56 chamber in order to handle longer for thier weight tracer bullets.

It is shorter in a .223 chamber in order to improve accuracy with varmint type bullets. Since tracers are not loaded in .223, the leade doesn't need to be long enough to handle them.

I stand corrected. Point taken.
And you explained it better than any others I've heard.

And the chamber differences are such that while people often talk about a 223 chamber

Ha! I first read this to say.......such that WHITE people often............
I did a double take, and thought, "That's not very nice."

 

[benzy2]

I don't believe much of anything made today in .223 is followed close enough to be dangerous with 5.56. It's one of those things where the obvious difference in the two is too hard to see that any lawyer wouldn't allow a rifle to go out the door without being safe for both. I wouldn't doubt custom or semi-custom work may be a more true .223 chamber. This isn't to say you shouldn't verify both what ammo you are shooting and the safety of it in your rifle first, just that in today's times, a true .223 on a production rifle is too costly when something bad happens with a 5.56.

 

[Viper65fr]

In europe we shoot the 223 and the 5,56 equaly in fact the problem with the Nato ammo is for reloading. The primer not always like the small rifle primer.
The french FAMAS is a 5,56, the minimi is a 5,56 the HK are 5,56. outside dimension of the case are equal.

The lengh of the ammo is more a problem to fit the magazine than the chamber.
For class F we shoot the 77grs the 80grs and the 90 grs but in Practical Rifle we shoot the 77 Amax because of the M16 mag on our rem 700.

If for accuracy you need to be as close as possible of the lands you better have an AICS mag than a M16

 

[Lovesbeer99]

Sorry to stoke the fire but you are not wrong. They are the same round.

Anyone know what the sammi specs are for a 5.56 compared to a .223? Whar source did you get the data from?

 

[Carl N. Brown]

it isn't at all simple

Here's just some of the details I have come across.

.223 Remington was originally developed from the .222 Remington and .223 Remington Magnum varmint rounds, adopted to military service as 5.56 NATO and gradually replacing .222 Rem and .222 Rem Magnum in civilian popularity at least in the US.

Barrels marked .223 tend to be chambered and rifled for bullets in the original 45gr to 55gr weight range.

Barrels marked 5.56 tend to be chambered and rifled for bullets in 55 gr and heavier weight range.

Firing 5.56 rounds with bullets heavier than 55gr in a barrel marked .223 may raise the pressure due the chambering or may give bad accuracy due to the rate of twist for short varmint bullets not stabilising the longer, heavier bullets loaded in 5.56 rounds.

Also while original .223 sporting rounds were in the 40gr - 55gr range, custom made .223 rifles have been made for deer hunting and chambered and rifled to accept bullet weights up to 90gr. So not all .223 rifles are chambered and rifled the same.

Some foreign countries don't allow civilian ownership of military caliber firearms, so some military firearms are offered in .223 rather than 5.56. Sometimes the civilian marked .223 rifle actually is chambered and rifled for .223 bullet weights; sometimes tho' they are just 5.56 barrels marked .223 in compliance with the law and some foreign enforcement authorities don't care as long as the letter of the law is complied with.

Wikipedia citing Accurate Powder on .223 Remington
http://www.accuratepowder.com/data/...al(5.56mm)/223 Remington pages 185 to 187.pdf

....while .223 Remington ammunition can be safely fired in a 5.56 mm chambered gun, firing 5.56 mm ammunition in a .223 Remington chamber may produce pressures in excess of even the 5.56 mm specifications due to the shorter throat.

I added May emphasis since some .223 Remington barrels are chambered to 5.56 NATO spex. (The problem there is, it would take a qualified gunsmith to confirm it.)

Jungle #5 has the best advice: "The answer is: it varies by maker, and it is hard to determine without careful measurement. To be on the safe side keep military spec ammo out of non milspec chambers."

 

[Jeremy2171]

And back before the internet it was used interchangeably and no one cared....same for 7.62/.308.... (shakes head and walks off)

 

[Lovesbeer99]

The main reason people feel the 5.56 is different is because the mil spec cases are thicker in the salls so if you load the same power volume into a mil spec case and a commercial case the 5.56 could produce a higher pressure. But no mater what you do you should not exceed the specified max pressure regardless of the case you use. Re-read your load book and you'll see that is explained in the .223 (5.56) section of the load book.

To help this along, try weighing the cases of various manufacturers and you'll see some are heavier then other and typically the LC cases are heaviest. If the external dimensions are all the same you have to conclude that the wall thickness is the difference. Either way when you work up loads you need to check for signs of pressure problems.

The .223 has a max cup of 52,000. I have yet to find a spec anywhere for a 5.56 that is different than this. Chambers and barrel twist are different for different reasons but the cartridge limits are the same.

 

[helotaxi]

Anyone know what the sammi specs are for a 5.56 compared to a .223? Whar source did you get the data from?

There are no SAAMI specs for 5.56. SAAMI doesn't recognize it as a sporting cartridge. Same with 7.63x51. SAAMI recognizes and has specs for .223 Rem and .308 Win. .223 is a lower pressure cartridge than the CIP specs for 5.56 (and CIP and SAAMI differ in the measurement methods). The two are not interchangeable. The cartridge prints are identical. The chamber prints are quite different. The max pressures are quite different. The 5.56 cartridge loading produces a higher pressure in a chamber designed to reduce pressure. Fire the higher pressure cartridge in the tighter chamber that doesn't have such a design and the result is pressure well beyond the max for the 5.56. I've seen tests with pressures in the high 70k-low 80k PSI range. The max acceptable pressure for any cartridge is 65k PSI per SAAMI; CIP for 5.56 is 62k and the .223 is a 55k round.

Call them interchangeable if you want but stay at the other end of the firing line from me if you insist on shooting 5.56 in a .223 rifle.

 

[helotaxi]

The main reason people feel the 5.56 is different is because the mil spec cases are thicker in the salls so if you load the same power volume into a mil spec case and a commercial case the 5.56 could produce a higher pressure. But no mater what you do you should not exceed the specified max pressure regardless of the case you use. Re-read your load book and you'll see that is explained in the .223 (5.56) section of the load book.

To help this along, try weighing the cases of various manufacturers and you'll see some are heavier then other and typically the LC cases are heaviest. If the external dimensions are all the same you have to conclude that the wall thickness is the difference. Either way when you work up loads you need to check for signs of pressure problems.

The .223 has a max cup of 52,000. I have yet to find a spec anywhere for a 5.56 that is different than this. Chambers and barrel twist are different for different reasons but the cartridge limits are the same.

This is all bad info except the 52k CUP for the .223.

Brass varies by manufacturer, yes but LC is actually some of the lightest. PMC, FC and Win/W-W .223 and 5.56 brass are identical within their brand. Lapua .223 brass is the thickest and heaviest out there.

The pressure spec for 5.56 is listed on the right side of this page. http://en.wikipedia.org/wiki/5.56x45mm_NATO

 

[benzy2]

Call them interchangeable if you want but stay at the other end of the firing line from me if you insist on shooting 5.56 in a .223 rifle.

The question still remains, is anyone today producing a true .223 chamber, or is everyone producing a 5.56 chamber and stamping .223 on the barrel. If you know for certain your barrel is only cut and designed for .223 pressures, then I'm with you. In today's lawsuit happy world, I have a hard time believing that anything sold in the US is leaving the doors with a chamber that is inappropriate for 5.56, outside of maybe a couple small shops doing specialty work for people specifically looking for a .223 chamber.

 

[rcmodel]

The .223 cartridge was introduced as a commercial cartridge in Jan 1964 by Remington.
One month later, it was adopted as the 5.56 NATO by the Military in the then new M-16 rifle.

At that time, short leade .223 commercial rifles with 1-14 twist barrels were all that was available. Some time later, Colt begin selling the SP-1 AR-15, and Ruger introduced the Mini-14. The Colts were marked 5.56, and the early Rugers were marked .223 Rem.
Both shot 5.56 GI ammo just fine.

In all the years since then, I have only heard of a couple of instances where firing 5.56 in a .223 Rem caused a problem.
Both cases I recall were with Remington 40-X Benchrest rifles with very tight, minimum spec benchrest chambers. And the only result was loosened primers.

I have never heard of any other problems with any other brand or model of .223 rifle in the insuing 46 years.

And back then I, and many others were getting our .223 Rem ammo direct from the source, Unkle Sugers 5.56 NATO supply channels!

rc

 

[X-Rap]

I have almost a dozen guns in these .22 cal chambers and have interchanged for 30 yrs without incident.
I use factory 223, surplus 5.56, and mixed brass to reload with the consistent charge of 25 gr. H335.
This mix has gone through semi auto, pump, bolt and single shot without a hint of pressure or harm to the brass or gun.
Put me in the doesn't matter category.

 

[Lovesbeer99]

So help with some math. I listed the max .223 as 52K cup but another poster had it as 55K. According to Wikipedia the max pressure of the .5.56 is 62,336 PSI which translates to 53K cup.

Also the internal demensions of a cartridge don't matter much if you know what you are loading and don't exceed the pressure limits. YOu can just as easily overload a commerical case as you can a mil spec case. If the previous poster is correct about the Lapua brass than that brass can produce higher pressures than the Mil Spec Cases. So you have to be more carefule and start low and workk up checking for pressure signs along the way.

Also, the chambers in .556 and .223 are different because of different shooter requirements, not because the rounds are physically different.

 

[Bartholomew Roberts]

The question still remains, is anyone today producing a true .223 chamber, or is everyone producing a 5.56 chamber and stamping .223 on the barrel.

Not only is hardly anyone producing a true .223 chamber; but many of the chambers marked 5.56 aren't true 5.56 either. Most of the manufacturers use a hybrid chamber of some sort and each one will have their own variation.

As to problems produced by firing 5.56mm in .223 chambers, the one common problem I see is that it can screw up the timing/pressures on an AR15 and you get failures to extract and/or eject. I haven't seen any issue more serious than that, though that issue can be pretty serious depending on the context of where it happens.