Stupid question of the week: is M855 safe in ARs?

[MarineOne]

My Bushmaster is stamped NATO 5.56 1/9. I've shot both 5.56 and .223 from it with no problems.


Kris

 

[1 LT MPC]

I've got a Colt AR 15A2 HBAR marked .223 on the receiver and 5.56 on the barrel. What's up with that? I never noticed it before but I purchased the rifle new around 1991. I assume it'll shoot both. My dad had it until he passed and it's never been fired.

 

[rcmodel]

Colt used to mark all their commercial AR-15 semi-auto receivers .223 to differentiate them from M-16 full-auto receivers marked 5.56.

And like I noted in my earlier post, back then there was not an SAAMI warning about the difference, as there wasn't much difference..

Later on there were also H-Bars made with stainless steel match barrels chambered in .223, as well as similar ones in 5.56.
Only the barrel marking told the tail of which one it was.

rc