Reit38

dumb question but is a 5.56mm and a .223 the same size cartrige? i bought a s&w ar15 today and wanted the box said .223 but i took out the gun and it says 5.56mm on it?

Texasyukon

I have been reading some on the AR15 and what i have been seeing is that they are the same. I am sure that you will get others on here to break it down for you.

corey012778

reit, just go into an gunshop, look close at and wolf (not saying buy) 5.56×45mm right under (.223 rem) then look at umc or what ever usa made. .223 rem (5.56×45mm),

http://www.ammo-oracle.com/body.htm

4th paragraph down

halcon

They both have the same demensions , but the 223 Remington is loaded at a lower pressure than the 5.56 military round . It is not reccomended to shoot military 5.56 rounds in arifle chambered for 223 Rem. At least that is what I have read . They just ran a article on this in shotgun news . I found this out the hard way myself , didn't hurt the rifle but blew some cases . Duh

BigTiny

I shot both versions out of my Saiga, but it was an AK variant. AR's can be more picky. I have only shot gub'ment ammo out of an AR.

Ruger-Redhawk

This is really strange. Just a couple weeks agoI got a reply from Ruger over this same question.I had written Ruger a letter asking if the 5.56mm was safe to shoot in a gun chambered for the 223 Rem.I askedabout using it in the Mini 14's and the M-77.They said that their rifles are chambered for the 5.56mm and either could safely be fired it these rifles.A couple years ago I bought two cases of Lake City 5.56mm Ball.That'show this question came about. Some said it's safe other said don't shoot it. Ruger tells me it's safe to fire in their rifles, I assume it's safe in all the one's chambered for 223.I have a Winchester Coyote in 223 and I will run the 5.56 through it.
Before hearing back from Ruger I asked a old friend who was a gunsmith before retiring. He was also a rifle builder. I asked him this same question and he said they were the same cartridge and interchangeable.The 5.56mm was a military designation for that round.
That'sproof enoughfor me.

nvshooter

The 5.56 round is loaded to higher chamber pressures than the .223 commercial round. Therefore you can shot both rounds out of a barrel chambered for 5.56. It is not a good idea to shot 5.56 out of a barrel marked .223.

RLoving1

But if you look in the Sierra manuel it shows more of same powder in 223 verses the 5.56!Confusing to me but mine is stamped 5.56 so I can sling both! I think the mil spec chamber is different,a bit more jump on bullet?

mxwarrior989

The difference is the amount of powder
its the same caliber bullet
but different amounts of powder

you can buy a book to look up the kind of powder and the amount of grains in it

Bullets come with different kinds of powder that have more or less "kick" to the amount

so if you buy a book and its the same power level with the amount of powder
you could do both
but if i was you
id stay with the bullet it says
or you could end up blowing up your gun with your face to it with a very small mistake

rickdavis

I wouldn't recommend shooting 5.56 in .223. 5.56 is loaded to a higher pressure and could cause problems. I hate hearing supposed gun experts telling others it's ok that they are the same. Example. My younger cousin and I went into a gun store in his home town on a lunch break from deer hunting.He's been wanting an ar since he shot mine. He asked the dealer if the one he had was 5.56 or .223 since he has a bunch of 5.56 that was given to him. The dealer stated that they we're the same. I told him he was wrong and he started rambling on about military and other stuff. Asked if I was in the service. I said no I just like my ar's and didn't want to see my cousin get hurt or tear up his rifle. We didn't end up buying anything from him. He did order a nice bushmaster the next week though.