Which crimp do I use?

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Which crimp do I use?

Category : Reloading

The first answer is that the TYPE of crimp is always built into the bullet seating/crimp die or the separate crimp die if it’s different from the seating die. So, for a 357 Magnum three die set (full length sizing die, bell mouthing die, seating/crimp die), the ability to roll crimp (which is the proper type of crimp for that cartridge) is built into that third die. Similarly, the third die in a 9mm Luger set is designed to taper crimp the bullets in place.

Any time you stretch the case mouth to install a bullet, you should crimp.

However, there are times when you do NOT want to crimp. Such is the case of necked or bottle necked rifle cartridges. When the necks of these cartridges are properly sized, there will be enough friction between the case neck and the seated bullet to hold onto the bullet long enough for all the powder to be burned inside the case, before the bullet leaves the case mouth. In those instances, the bullet seating/crimp die should be adjusted so that the crimp portion of the die does not touch the case mouth.

Here is a chart, which gives you all of the possible crimp situations, and suggests the proper type of crimp for that cartridge.

Crimping Chart

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