[quote]Originally posted by Artsi:
<strong> Job that crimp will do is to hold bullet still while gun recoils. That will discourage bullets from sneaking outwards, thus increasing ammo overall lenght. That in return will cause malfunctions whether be it revolver or autoloader.
-Artsi</strong><hr></blockquote>
Yes....... and no. In a revolver, the bullet will tend to creep forward under recoil. A roll crimp will prevent it.
In an auto-loader, however, the bullet will be pounded deeper into the case and raise pressures. This is especially true of the 9mm.
The bullet in a revolver tries to remain in it's place while recoil snatches it rearward and attempts to pull the case away from it. Without a roll crimp to hold it in place, the bullet will move forward.
In an auto-loader, the whole cartridge tries to remain stationary while everything else recoils sharply to the rear. That brings the bullet violently into contact with the magazine's forward wall and will push the bullet deeper into the case. The easiest way to see this clearly is to load five softpoint cartridges into a bolt action rifle and fire the first four. Then check the nose of the fifth and note how battered it's become.
Some factory cartridges in 9mm will have a crimp ring around the case immediately below the base of the seated bullet. (Remington is one that does.) The crimp ring becomes a waist that is smaller than the portion of the case in front of it. It's sole purpose is to prevent the bullet from being driven deeper into the case under recoil.
Some older rifle cartridges intended for use in tube-fed rifles have waist crimps and mouth crimps because the cartridges are subjected to both forces under recoil.
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