Not always possible, but sometimes on the trigger guard you can use a large dia blunt punch to upset the countersink from the backside of the guard.
That pushes metal upward into the countersink inside and makes the screw tighten up as it pulls into place taking the over timeing out.
I use a a round nose punch large enough to span the screw hole plus the countersink on the backside of the hole. Support the guard on a flat steel surface of course and take it easy as it's quite easy to push metal inward.
Many countersinks are thin there and don't take much effort. The guard will bend very easily at the screw holes too so be careful.
It also works on trigger plates and other parts if the same conditions are there for reworking. Even thin case hardened surfaces dimple inward OK but don't over do. If in doubt use a shim here.
Couple ways to shorten up the TPI on machine screws to make them draw in quicker. That corrects over timing. Also drawing out same to allow timing w/a screw that comes up short of 12 oclock.
Certainly not professionally endorsed! but I've used it for 40yrs and will continue to. No complaints so far.
