How much crimp?

Reloading your own ammunition is not a task where creativity comes into play.  We are working with components that, when used correctly, can be used to create ammunition that is as good or better than factory offerings.  As an added bonus we can frequently make this ammunition at significantly lower costs than comparable factory offerings.  There is, however, an element of responsibility that cannot be ignored.  We have to follow safety procedures.  We have to follow the “recipe” for the load we are making.  We have to use “best practices” at all times.  Sound ominous?   Well, it is and it isn’t.  If you are willing to accept that this is serious business and that your attention has to be on the task at hand then reloading can be a safe and even fun hobby separate from the fun of shooting the rounds that you make.

One of the things I often hear people talk about at the range is crimp. How much? How little? How do you know? Well for those using a taper crimp, and pretty much all semi auto cartridges are going to fall into this camp, the math isn’t that hard. Get your dial calipers out, you die hard/perfectionists can grab your micrometers instead, and measure your bullet diameter and the case wall thickness of your empty brass. With those two numbers use this formula:

bullet diameter + case wall thickness times two – .001

So for my 9mm reloads I’m looking at:

.355 + .010(2) – .001 = .374

I do want to add that the .001 is the amount of crimp we are applying and you can adjust that to .000 if you want no crimp, just a straightened out cartridge, or .002, or greater, if you want a heavier crimp.  Some of our technicians report that plated bullets are prone to fail if they go beyond a very light crimp.

You can also try our Crimp Calculator if you want to skip on doing the math.

Then it’s just a matter of following the setup directions for the crimp die. Manuals for our presses are here.

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