Thanks for buying a DPMS!
Here is a list in order of importance on a new rifle that was test fired from the factory not locking back/malfunctioning.
1.no oil/under lubricated
We get calls all the time on this, for some reason the "experts" say to not or barely oil the rifle. The new rifle BCG must be generously oiled with regular gun oil. No grease (to heavy), no Rem-oil (to light) just regular oil and "the wetter the better".
2.bad ammo (steel case/surplus)
You spent hard earned money on the rifle, don't skimp on the ammo. Use only brass cased American made ammo.
3.BCG break-in not complete 100-150 rounds
Just like a new car it needs to "loosen up" and break in. This is not a 40 year old issue rifle that's well broken in, it's brand new machined to tighter tolerances and needs to be shot.
This fixes the problem 99.9%.
Any questions give us a call