Some benchrest shooters do lightly crimp ther bullets to obtain consistant pressures, or by seating the bullet to contact the rifling. It is said that crimping does not hurt accuracy if it is done right, and it may help it. I don' t crimp if I don' t have to. One can buy a tool called the Corbin HCT-1 for handloaders to add their own knurled type cannelure it can also be used to cannelure the case. It cannnot be used on solid bullets. Good luck.