[Roadwild17]

What are the differences between .223 and 5.56mm? I know 5.56 has higher pressure, but what does this mean in terms of ware on the rifle? Wll the gun blow up if I shoot a high # of 5.56?

[ny32182]

The brass dimensions and the overall cartridge dimensions between the two rounds are the same. 5.56 operates at slightly higher pressure.

The .223 chamber is cut slightly tighter than a 5.56 spec chamber.

General rule is that .223 is ok in a 5.56 chamber, but 5.56 might not always be ok in a .223 chamber.

[TimH]

Check out here:

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

and here:

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

[Red Tornado]

Threre's lots of great info there, Tim, but it looks like everything is concerned with ARs and auto loaders. Is there an issue if I use 5.56 in a .223 chambered Handi-rifle or bolt-action? (One of these is on the horizon) Won't these platforms negate the potential problems with the different chamber sizes?
Thanks,
RT

[Cesiumsponge]

In addition to the pressure, its commonly cited (not by me, but "them") that SAMMI spec .223 is where all the match-grade stuff is and in general, more accurate than offerings in 5.56mm NATO which is usually milspec/milsurp stuff.

There are three schools of thought in the increased pressure. Some people have squeaked away with shooting 5.56mm in a .223 chamber/barrel with no issues. Some have occasional signs of brass getting stuck and feeding issues due to slightly different sizing but they can put up with it. The last school of thought jump up and down about it blowing receivers up.

[mete]

The biggest problem is the throat. The 5.56 has a longer throat to handle the very long military bullets.Shooting these rounds in a short throated 223 chamber causes very high pressures !!

[Mike Hull]

I would really like to see documented proof of any .223 bolt gun, in good condition, that blew up shooting 5.56 rounds in it.
I'm talking about factory loads, and not somebody's reloaded military brass where they didn't cut the load down by 10% to make up for the thicker brass, and smaller capacity.

In fact, I'd like to see that same proof for any rifle in good condition, chambered for .223, that blew up firing it's military counterpart.

I worked in the firearms field for many years, and I've never even heard of one. :confused:

[Mike Hull]

The biggest problem is the throat. The 5.56 has a longer throat to handle the very long military bullets.Shooting these rounds in a short throated 223 chamber causes very high pressures !!


You mean like Remingtons?

The throat on my LTR is so long, that I can't load bullets out far enough to touch the rifleing, and still fit in the mag.

I'm talking bullets of 69-77 grains here, not shorties like the 50-55 grainers.

Most civilian factory guns have fairly long throats.

[jefnvk]

The biggest problem I ever hear of, is that the .223 chamber is cut to tighter specs, that 5.56 can get stuck in there.