problem loading m1 carbine

[Rocky Raab]

The problem is because it's a straight-wall case.

If it were a bottleneck, the expander ball would be bringing the neck diameter back up a bit - just enough to fit the pilot of the trimmer.

But a straight case has no expander ball in the sizer, so the case is being sized down too much for the pilot. You need to run the cases through the expander die after sizing. They should then fit the trimmer pilot precisely. If they are still a bit snug, try buffing down the pilot with crocus cloth with the pilot spinning in a drill. Also be sure to use just a whisper of lube on the pilot every ten cases or so while trimming to keep it from galling the inside of the case necks. Just touch the pilot with an oily finger - you don't want any visible amount, just a film.