I agree with 2hot2handle, when dry firing I ride the charging handle back to ease the impact of the carrier slamming forward but I let it slam forward when chambering a round.
Hopefully it's just the buffer retainer pin that's damaged - not the hole in the threads?
The biggest issue with assembling an AR isn't so much getting the parts together right - it's getting the right parts together.
You'll remember the quality of a gun long after you forget how much you paid for it.
US Army 1966-69, VFW Life Member, Retired Geek