I and several others on this board had a problem with DPMS parts kit pivot and take-down pins, but I can't find the post (May'04 posts archived?).
Basically DPMS parts are good, but they must have had a run of out-of-spec pins.
Both were completely unusable without major fitting headaches and filing.
I replaced them with spares, and it was only an issue in 1 of the last 4 DPMS parts kits I've used lately. One kit, both pins; I believe there was a MidwayUSA retailer connection as well, but don't recall. (no fault of Midway's -- the kits were sealed DPMS parts kits.)
Independantly of DPMS, most of my stock triggers are gritty until broken in a bit.
Try the polishing recommended in the "15 minute trigger job" posted somewhere on this site -- it really makes a difference.
Cheers, Otto