Thin-brass RP's...
Ole Farmer Buck--I solved the problem w/o modifying my sizing dies, buying new dies, or buying different-diameter bullets--I just quit using RP brass!
I reload .357 Magnum cases with LDEWC's loaded to .38 Spl levels, for bullseye shooting. What with the RP cases having thinner walls (more room for gas expansion as the powder burns) and holding the bullets less tightly (thereby letting the bullet move before the burning powder gases get up to normal pressure) both of which would affect the velocity of the bullet, and therefore the POI, I have stopped reloading RP cases.
No idea exactly how much it affects actual performance on the range, but I feel more confident NOT using the RP's, so it's better for me.
All the other brass reloads and works just fine except of course the Amerc brass which is trash. That, and now the RP's I find @ the range, goes straight into the recycle bucket.