I haven't fooled around with ARs very much but I would llke to get a nice accurate upper for my RR lower for some coyote hunting.
Since I have been looking, I've noticed some advertised as 223 Rem. chambered and others listed as 5.56 NATO.
Why and what is the difference?
The throat?
Any advice on barrel makes and configurations? I was thinking a 18" stainless if I can find one. I would like to keep the weight down. (I may have to stay with a 20" barrel)...any thoughts?

The 5.56 chamber allows the use of higher pressure milspec ammo. The commercial.223 is a tighter chamber and supposedly more accurate.

There is also the .223 Wylde which is a hybrid in between the 5.56 and .223.

You can shoot 223 in 556 chamber.. but you could have pressure issues with 556 in 223 chamber... I just use wylde chambers in the ones I would like to be more accurate...

You can "find" ar barrel from 7.5 to 38 inches

Thanks guys.

We have 223 rifles from many different manufactures, and we shoot standard military ammo in all of them.

Never encountered any high pressure problems.

.223 Rem
5.56 Nato
.223 Wylde

Are all very very similar with tiny differences

The 5.56 has all the same dimensions as the .223 Rem but with more free bore to allow bullet jump

The .223 Wylde shares all the same things as the 5.56 chamber but with less clearance in the neck diameter

That's it!!!

If one does a bit of searching, they ca find many arguments regarding the 223/556 556/223 question.

Some sources will say "fagetaboudit" and ease your mind to load up and fire away (556 ammo in 223 Rem chambered guns) while others will recommend the opposite. It is well known that the 223 rem chamber ha a rather short lead/throat and operates at a lower SAAMI chamber pressure, while the 556 and other modified versions of the 223 ( Wylde, AMU, Match etc) have a more generous throat lead and even body. One source pressure tested M193 55 grn US ball in a 223 REM chambered pressure barrel and found the average chamber pressure ran at ~75K psi.

The 556 family of ammunition runs a different pressure spec- 63250 psi measured at the mouth or throat vice the 223's 55k psi at the chamber body- a difference in location reasonably enough to assume that the chamber pressure of the 556 family exceeds the 55k of the 223 rem.

What is your rifle designed for?

What does all this man?

Well, if you want to fire 556 in a standard 223 rem, you are basically risking firing pressure test/proof loads in your arm every time you pull the trigger. Does one need to make a recommendation? Though not.

Best.

quote:

Originally posted by Saeed:
We have 223 rifles from many different manufactures, and we shoot standard military ammo in all of them.

Never encountered any high pressure problems.

I had a Savage 24V chambered for .223 that would not fire 5.65x45mm. For awhile I thought the surplus ammunition was bad, but it worked fine in a Mini-14.