What did I buy? AR .223/5.56 question

[Guest pusherman]

Sorry if this is a dumb question-

I got a Colt AR15 in about '96. I HAD to have a black rifle, so I got just picked one. I know... not so smart. But at the time that damn assault ban was in place and I couldnt afford a pre-ban rifle.

At the time I assumed 556 and 223 where the same round. I've learned a bit since and I know now thats not the case. Something about bullet length or head space and chamber pressure.

Anyway, stamped on the lower is this -

Match HBAR

CAL. 223

ser CMH 025xxx

But on the end of the barrel is this

C MP 5.56 NATO 1/7 HBAR

So, is this a .223 or a 556? What the heck did I buy?

thanks in advance!

-Jason

[Guest Todd@CIS]

It's 5.56mm...so you're OK shooting both.

[TNFF319]

I was told go by what is on the bbl.

[Smith]

5.56. The difference is in the chamber/barrel. That's why you go by the barrel stamp. BTW you can shoot .223 in your 5.56.

[50 cal]

You have a 1-7" twist barrel. You can shoot the heavier bullets such as the 77 grain bullets and they will stabilize just fine.

You can shoot the lighter bullets also, just the heavier stuff will stabilize. You will pay a premium for the heavier bullet ammo but it is worth it.

Yes, you can fire .223 ammo through it no problem

[mj12]

So, is this a .223 or a 556? What the heck did I buy?

They're essentially the same round. 5.56mm is the NATO designation, and .223 caliber is the for us that don't use the metric system. Edited April 7, 2010 by mj12

[Guest bkelm18]

So, is this a .223 or a 556? What the heck did I buy?/QUOTE]Essentially the same round. 5.56mm is the NATO designation, where .223 caliber is the for us that don't use the metric system.

No they are not the same round. 5.56 is loaded to much higher pressure than .223. Same physical shape and size for the most part, but much different pressures.

[Guest Todd@CIS]

They're essentially the same round. 5.56mm is the NATO designation, and .223 caliber is the for us that don't use the metric system.

If this were true, this thread probably wouldn't exist.

SAAMI considers firing 5.56 in a .223 chamber an unsafe practice.

http://www.saami.org/specifications_and_information/publications/download/SAAMI_ITEM_211-Unsafe_Arms_and_Ammunition_Combinations.pdf

Edited April 7, 2010 by Todd@CIS

[Guest pusherman]

I guess the question I still have would be why the lower is marked .223 and the barrel is marked 556 NATO.

[piglet]

The lower is a part that is for use in rifles sold in the USA. the 5.56 barrel is used for rifles sold world wide. I use 223 in barrel stamped 5.56 but not the reverse. pressure is not the same size is not exact same

[kesava]

EXACT same size, metric vs u.s. meas. anyone who tells you different has no idea. The throat isnt different, its not taller, the case wall thicker, however it doesnt alter the shape of the case. they give you BOTH in iraq for .223 rifles. Pressures are slightly different but not enough to impact ballistics in a major way. All modern rifles (1990+) can handle both. I contracted with a large gun manufacturer, pimped them for information on coffee breaks.

Edited April 7, 2010 by kesava

[Guest manofsteel]

my dpms is the same, lower 223, upper is 5.56. i shoot 223 ammo of all types, so far no problems. seams to really like federal best:up:

[Schadenfreude]

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

also my speer reloading manual says "shooting 5.56 in .223 rifles results in excessive pressure"

[Schadenfreude]

also see The Gun Zone -- 5.56mm ammo FAQ v1.14

& The Gun Zone -- .30 Caliber Ammo 308 vs 7.62 x 51

[TN-popo]

EXACT same size, metric vs u.s. meas. anyone who tells you different has no idea. The throat isnt different, its not taller, the case wall thicker, however it doesnt alter the shape of the case. they give you BOTH in iraq for .223 rifles. Pressures are slightly different but not enough to impact ballistics in a major way. All modern rifles (1990+) can handle both. I contracted with a large gun manufacturer, pimped them for information on coffee breaks.

I guess you know better than SAAMI and all the major ammunition manufacturers.

Edited April 7, 2010 by TN-popo

[Farman]

Are all over the counter ARs sporters, SAAMI chambered? Are some military chambered and head spaced so they can safely fire 5.56?

[Smith]

Are all over the counter ARs sporters, SAAMI chambered? Are some military chambered and head spaced so they can safely fire 5.56?

If the barrel is stamped 5.56 it can shoot both if it is stamped .223 it should only be shot with .223. Most AR's can shoot both. Usually only the hunting oriented or target specific rifles are stamped .223.

[I_Like_Pie]

I guess you know better than SAAMI and all the major ammunition manufacturers.

As a reloader and one with an understanding of how SAMMI Derives their data.

Yes....Yes I do. I am somewhat ashamed that the people here at TGO lack the critical thinking to do the same. It is very simple actually, but it is easier to tell people "don't do it" rather than try to explain to people that can't understand. Has to do more with the history of the guns chambering the cartridge rather than the cartridge itself.

[50 cal]

Just go here for all your 5.56 and .223 ammo questions..

The AR15.com Ammo Oracle