With many semi autos, you will need a small base sizer die in order for them to chamber. Trimming the cases is also very important when making ammo for semi auto rifles. Headspace is the distance from the bolt face to the part of the chamber that stops the round from going in too...
HILLIARD APPRECIATES HOW FORTUNATE HE IS GIANTS RECEIVER ALMOST HAD HIS CAREER ENDED BY SERIOUS NECK INJURY.(Sports)Rasizer, Lee