Whats the difference between 5.56 Nato and .223 Rem?

[albanian]

I thought they were the same thing but on Model 1's wesite, they let you choose what type of upper you can order. I also saw a thread over on AR-15.com that some guy was saying that his 5.56 Nato Ar wouldn't feed .223 Ram ammo well.

What is going on? I thought they were the exact same thing but now I am not sure.

 

[ny32182]

www.ammo-oracle.com

The chamber dimensions are a little different... the 5.56 isn't quite as tight, for better extraction reliability. An AR chambered for 5.56 can run .223rem with no problems, but the opposite is not always true.

 

[dghboy315]

thanks, i always wanted to know that too.

does that mean that you should buy ar's in 5.56? i just traded for one, i wonder which it is. it's a DPMS M4 profile. i'm assuming that most US guns are 223.

 

[Coltdriver]

I too did not know that there was a difference, even when I bought my AR years ago.

If I were ordering an AR I would only get it in 5.56. The only reason I can think of for getting one in .223 would be if you were going to target shoot.

It is true that you can run .223 ammo in a 5.56 chambered rifle. The reason we are warned not to go the other way around is that a 5.56 round is crimped and may present higher pressure is intended for a .223 chambered rifle.

That is a bit of stretch if you ask me, but the warning stands.

In every other aspect except the crimping and perhaps slightly less case volume in the military version there is no dimensional difference in the ammo.

 

[Bartholomew Roberts]

does that mean that you should buy ar's in 5.56?

The only time I'd go with a .223 SAAMI spec chamber on an AR is when the absolute best accuracy was the number one priority of the rifle.

I've yet to see where firing 5.56mm in a .223 chamber caused unsafe pressures; but I've seen plenty of examples where the higher pressure lead to malfunctions. Brass in the ejector, ripped rims, short stroking, primers blown out, bolts and cam pins breaking prematurely.

 

[Steve Smith]

Even the popular (for match shooters) Wylde .223 chamber is oversized compared to a .223 spec reamer.