I can't think of anyone in SC, most of the time my buds make me tinker with their stuff. I remember we swapped a few parts at the last fall shoot but it failed to help.
Could be because those parts were from Jeff's 53 built on a SW receiver by a custom builder.
I sold my V53 so I'm of no use as a parts donor. Now this year we might have another Vector donor rifle to pluck parts from if M16MANIAC attends.
I built my own mp5 in semi ....There are a few things that I would look at bolt/ trunion head space, also checking the buffer, is the bolt dragging in the receiver? Run A 100 rds. of +p ammo in the weapon the weapon system ...they tend to need a break in period. Tom