Expand Mandrels for Bullet/Neck Tension Builder
Subtract the 0.004" from the standard bullet diameter, 0.284"-0.004"=0.280", this will be the final size after expanding. However, the neck inside diameter needs to be slightly smaller so the expand mandrel can properly size the brass. Now subtract the 0.002" or 0.003" from the final size, 0.280"-0.003"=0.277".