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Bulleting and Crimping Stage of Reloading ammunition

Bulleting and crimping of reloaded ammunition rounds are usually combined into one operation that uses a two function die.

Bullet seating punches have noses that are shaped internally to match the bullet that they are intended to be used with, these may be purchased from die manufacturers or machined from blank punches by the reloader.

Adjusting a bullet seating die

Many bottleneck cases do not require a crimp as the friction fit of the case mouth can be sufficient hold the bullet in place. Crimping the mouth of the case causes fretting and shortens case life.

Basic bullet seating and crimping die Seating bullets requires accurate adjustment of the seating punch...

Adjusting a roll crimp bullet seating die

Revolver cartridges generally require crimping to hold the bullet firmly in place during recoil, such bullets must have a crimping cannelure to act as a receptacle for the crimp.

Consistent roll crimping relies on the cases being identical in length, wall thickness and chamfering.

For bullet seating and crimping in one operation, adjust the seating die as follows...

Adjusting a bullet seating die for taper crimping

Cartridges for auto pistols headspace on the case mouth and are generally taper crimped in order to retain this feature. Taper crimp bullet seating dies are specially marked by their manufacturers to differentiate from roll crimping dies.

The taper crimping feature is part of the die profile and the amount of crimp is determined by how far the seating die is screwed into the press. Cases to be taper crimped should all be the same length and wall thickness, but bullets do not require a crimping cannelure.


  1. When adjusting overall cartridge length, the bullet must not touch the rifling when chambered.
  2. If reloading a type of round that may be used in several different weapons, the dimensions of whose chambers may be different. The safest procedure is to set the bullet to the cartridge overall length as specified in your reloading manual or to repeat the setting operation for each weapon and select the shortest as your standard for that group of weapons.
  3. If you have a factory loaded cartridge available, it can be used as the sample cartridge in setting up your die, providing that the bullet in the sample is identical to that which you intend to use.
  4. The crimping feature is machined into the seating die and the amount of crimp is determined by how far the die is screwed into the press. Bullets can be seated without crimping by setting the body of the die a half turn shy of the case mouth.
  5. Setting the seating die too far into the press will cause an aggressive crimping of the case and may result in bulging of the body of the case.

 Written... 21 January 2007, Code Altered... 18 May 2008,
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