There must be enough tightness on the bullet to hold it for proper ignition of the powder !! A crimp alone is not enough . Holding a cartridge firmly in your hand push down on the bullet .If , without too much force you can push the bullet into the case you don't have enough grip on the bullet. It's not only a crimp !! You may need a smaller expander die .If you need more then use a crimper , roll crimp for bullets with cannelure and taper crimp for plain bullets ! Lack of enough force holding the bullet will cause poor accuracy and permit bullet movement in the case .Too much crimp will create poor accuracy !
