Okay I know this is an idiot question but.

[BadShot]

And cause I'm still a little too ladled with pain killers and my search-fu is asleep..

What about the infamous .223 Wydle chambers?

[DocMedic]

One thing to be aware of is the difference between the Wylde and 5.56 NATO chamber in the freebore area before the bullet engages the rifling.

The NATO chamber is extremely forgiving. IIRC, it is .2260 - .2265 in this area, and the bullet is nominally .2240. Sort of like throwing a hotdog down a hallway. It keeps the pressures down, but doesn't guide the bullet into the rifling as well, with at least .001 per side between the bullet and the bore.

The Wylde chamber is nominally .2245 in the freebore area. That's almost nothing there. A little bit of crud on you bullet or barrel, and it's a slight interference fit. If you have ammo with long bullets like 75, 77 or 80 grain bullets, you'll notice this. Chamber a round by letting the bolt fly. Then extract it by hand. You'll feel some resistance (at least I do, with my RRA / Wilson barrel, with a Wylde chamber). That is because the bullet is sitting in that freebore area if your ammo is loaded to magazine length, and if the bore is a little bit dirty and the bullet isn't perfectly straight and centered in the cartridge case, it's dragging on the walls of the freebore area. If I haven't cleaned by barrel in awhile, it's considerably "sticky" to hand extract. Also, my RRA / Wilson / .223 Wylde barrel will blow primers on hot ammo (with 75 - 77 gr bullets), which won't in a 5.56 NATO chamber.

So, what is the "take-away? The NATO chamber is more forgiving of hot ammo and fouling. The Wylde chamber is better for target shooting but is less forgiving. There is no such thing as a free lunch. If you want "match accuracy" and shoot 5.56 NATO ammo, you get the Wylde chamber. If you don't care about "match accuracy", get the 5.56 NATO chamber.

found it on arfcom

[HBARleatherneck]

what docmedic said. the wylde chamber is tight

i can shoot wolf through all 4 or my other ars.

i can not shoot wolf through a RRA HBAR upper chambered in .223 Wylde

i can, but it doesnt extract reliably (read bolt face stuck in chamber)

i know some of you are too good to shoot wolf and question why I am shooting it, but its cheap. I load my own ammo, but sometimes I just shoot it.

[Hoosier]

My AR doesn't have a clear label on the barrel, but it will only properly cycle M855 NATO 5.56 ammo, every .223 round FTE or the next round fails to chamber.

H.

[Daniel_187]

I have some once fired brass .223 and 5.56 and messured them with the cailipers and the 5.56 was a little bit longer the .223

[HBARleatherneck]

that is common.

from one manufacturer to another
from one lot to another
from one powder charge to another.

the cases grow at different rates.

[DD977GM2]

Here is a great source for anything related to 5.56 NATO or .223 ammo.

http://ammo.ar15.com/ammo/


As much as I can not stand the site, it still has its atributes for learning just about anything firearm related, especially ANYTHING for the AR15 platform.
FWIW, this is not a stupid question. It is a common question that I even have to reference from time to time as my memory sucks donkeyballs.