Home >> Collecting >> Gun Collecting

How to Measure Crimp on Cartridges

Loading ammunition at home attracts many hobbyists. Some do it for the money savings while others use it to experiment with various combinations to find which cartridge and components best fit their firearms and style of shooting. A vital part of making sure the bullet comes out of the barrel properly is to have a well-seated bullet in the brass. The point where the bullet and brass meet is the crimp. A crimp that is too loose will waste power and speed, while a too tight crimp may cut through the copper coating on the bullet, or distort its shape.

Things You'll Need

Calipers measuring in the 1000th of an inch range.

Instructions

- 1
  Measure the brass thickness at the case mouth with a caliper. Multiply this figure by two.
- 2
  Add the diameter of the bullet to the previous figure. This is the base, or zero.
- 3
  Seat the bullets into the brass using the crimp die.
- 4
  Remeasure the now complete cartridge again at the mouth of the brass.
- 5
  Compare the base figure with the second measurement. The difference between the two is your crimp measurement. Until the performance of the cartridge is measured by test firing it, you will not know if this is a good measurement or bad one, or if it needs to be adjusted higher or lower.
- 6
  Test the cartridge by firing it at a white sheet of paper at 5 feet distance. If powder burns are seen around the bullet hole the crimp is too loose and powder is escaping the cartridge before it is burnt. If the paper is clean and the bullet is otherwise okay then the crimp is close enough.

Gun Collecting