question about ar 15

[Guest brandon_pitt]

I just bought a built ar. Dpms lower, rra upper. 24" bull barrel, supposedly bushmaster, but isn't marked. My lower says .223/5.56. How do I know the upper can shoot 5.56? I've shot .223 through her just fine. Any help would be great. Thanks

[JeffL]

Check on top of the barrel towards the muzzle. It should be marked with the caliber and barrel twist. My Bushmaster is marked 1/9 5.56 NATO.

[Troutburger]

If its not on the barrel towards the muzzle, then it should be on the barrel underneath the hand guards.