5.56 NATO

About 5.56 NATO

5.56 NATO is the AR-15's native chambering and runs at higher pressure with a longer throat than .223 Remington. That difference is the single most important thing on this page: a 5.56 chamber fires .223 safely, but a barrel marked .223 Remington should not be fed 5.56. Read what is stamped on the barrel before you buy either.

Barrel twist decides what bullet weight your rifle will stabilise. A 1:7 twist handles heavy 77 grain match projectiles; a 1:9 shoots 55 grain beautifully and may scatter the heavy stuff. Rifles marked .223 Wylde appear on this page deliberately — Wylde is a hybrid chamber cut to take 5.56 pressure while giving .223 accuracy, so it is the one chamber that genuinely shoots both well.