To avoid primer backing out in a full auto and jamming things, they squeeze a slight lip in government ammo around the primer after it is seated. I think I saw a "stab crimp" used on Japanese ammo. All you have to do is remove this lip. Sharp pocket knife blade once around will do that nicely. BUT very Many cases and your fingers get tired.
I have also used the LEE neck chamfering tool, among others. Works, again, tired fingers soon...
For the wood workers... I have heard (by #) of a countersink for flat head screws that works great... Chuck it into any rotating device and touch the primer pocket to it. LIP GONE!. I jumped from Neck chamfer tool to die/punch... don't remember the #
RCBS and ch4d.com for sure have a die set where you support the case and use press leverage to force a pin that resizes/slips into the hole, the original size, and forms a slight taper, rounding for the ease of the insertion of the next primer at the edge. Dillion makes a small press device exclusively for this. Your bucks, your call... luck