Just pathetic.
WOW.....I have had 0 issues with mine. I have fired at least 1200 rds through it without a problem and I like shooting fast as well. I do have a vertical grip on my forend and let my left hand absorb most of the recoil (not the c-stock). All 3 notches seem to seat positively and when I shoot I have it fully opened.
I have heard where people are complaining about the finish chipping, but mine is not. Mine has absolutely 0 chips. IMO it looks awesome, it is a slightly different color than the M4. Pro Mag advertises a "Lifetime Warranty", my advise is send it back !!