Everything mentioned so far is spot-on and correct. You can't pre-seat the bullets, they are supose to be that tight a fit. A slight chamfer should do the trick.
Two other "tricks":
DO clean the shell holder recess. Gunk builds up and it can keep the case from centering in the shell holder, which runs it off center into the die. A nicked/dinged/burred case rim will do the same thing (OK..most cases are "rimless" but we'll call that part a rim anyway).
"RedNeckReloading". Keep a few military FMJ bullets on the bench. Pressing a .30 cal FMJ nose first, with just finger pressure, into a .243 case will slightly flare the neck. Comes in handy for loading plain based cast bullets.
Two other "tricks":
DO clean the shell holder recess. Gunk builds up and it can keep the case from centering in the shell holder, which runs it off center into the die. A nicked/dinged/burred case rim will do the same thing (OK..most cases are "rimless" but we'll call that part a rim anyway).
"RedNeckReloading". Keep a few military FMJ bullets on the bench. Pressing a .30 cal FMJ nose first, with just finger pressure, into a .243 case will slightly flare the neck. Comes in handy for loading plain based cast bullets.