Originally Posted by Robk
Not to make light of your issue, but are you using the right ammo? No mention if your AR is chambered in 5.56mm or .223. There is a difference. 5.56mm will stick in a .223 chamber and my be causing your issues. The 5.56 is just ever so slightly larger, by thousands of an inch, but it does not fit a .223 chamber well is tolerances are tight.
so, to sum up
5.56mm will not work properly in a .223.
.223 will work properly in a 5.56mm.
I'm sure if this is not the problem, others more educated on this subject will steer you right.
No sir. Some (heavy bullet) 5.56 can have a longer OAL that when chambered in a .223 'may' contact the barrel leade, but it's highly unlikely. For all practical purposes a 55gr .223 and a .55gr 5.56 are identical.
1. That portion of a firearm's barrel immediately in front of the chamber where the bullet travels prior to contacting the rifling.