I know when I tried to load the Winchester 64 PP and saw how easily they were moving I adjusted the Lee FCD to a pretty darn heavy squeeze and got them to hold. I was still scared of pushing a bullet in and creating a big pressure spike cause I always seat a mag and release the bolt to load. I checked the first 2 rounds I put into battery and found they were pushed back.
I'm not saying that happens to properly sized bullets that are being held by properly sized case necks, I can't, but I do think there are forces that could affect seating depth when the bolt moves forward into battery. Like MM said , you would have to eject and caliper a bunch of them to find out.
I think I could do that with ammo made up with no primer or powder. Without the minuscule chance of a slam fire I could test this at home. That would tell me about my sizing mandrel.. and the bullets I use.. in that one gun..you'all are on your own.
