Size expander plug .002 0ver bullet size. For a .366 dia. bullet use a .368 x .364 expander plug. this will give you .002 clearance to start your bullet and .002 neck tension.
Additional information
Weight
.25 lbs
Dimensions
1 × 1 × 1 in
368 Rifle Expander Sizes
368Cal (R) .368 x .364, 368Cal (R) .369 x .365, 368Cal (R) .370 x .366