Thread: Brass deformation - rimmed (303) vs shoulder (308)

The shallow shoulder design on the .303 causes it to “flow” more, and probably require trimming more, especially for warmer loads.

ZQLewis, the 99 has a rear locking action, and typically does require full length resizing, again this becomes more necessary with higher pressure loads. When I had one in .308 I could get away with two reloads just neck sizing, after that needed a full length. That was at book max.