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Ammo and Reloading Factory Ammunition, Reloading, Components, Load Data and more.

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  #1  
Old 09-23-2016, 5:30 PM
MarikinaMan MarikinaMan is offline
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Default New reloader checking crimp...

Pulled my dummy round after just setting my crimp.

The round goes in the case gauge no problem.

I was told to pull a bullet to check my crimp marks.

There is no crimp depression on the bullet except a hint of whiter metal where my crimp was.

Good enough?

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Last edited by MarikinaMan; 09-23-2016 at 5:54 PM..
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Old 09-23-2016, 5:32 PM
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Gringo Bandito Gringo Bandito is offline
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From the dillon precision facebook page...

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 - .004.

So for my 9mm reloads I'm looking at:

.355 + .010(2) - .004 = .371

(eta) I do want to add that the .004 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 .001 if you just want a very light crimp. Some of our technicians report that plated bullets are prone to fail if they go beyond a very light crimp.

Then it's just a matter of following the setup directions for the crimp die. Manuals for our presses are here: http://www.dillonprecision.com/manuals.html
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Old 09-23-2016, 5:35 PM
lost Bob lost Bob is offline
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Is it a plated bullet or FMJ? Is it 9mm? I usually measure case mouth right below bullet with my calipers to check "crimp" for auto loading rounds. It also needs to enter your case gauge or pass "plunk" test in barrel. The Gringos formula is similar to what I have used in the past- case mouth measures about .470" for .45 ACP

Last edited by lost Bob; 09-23-2016 at 5:39 PM.. Reason: update
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Old 09-23-2016, 5:46 PM
MarikinaMan MarikinaMan is offline
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9mm FMJs

Per that computation, I am on the dot. .377

Should I be worried about case wall thickness variation for range cases? My cases are coming in at .013.
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Old 09-23-2016, 6:24 PM
Bill Steele Bill Steele is offline
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Quote:
Originally Posted by MarikinaMan View Post
9mm FMJs

Per that computation, I am on the dot. .377

Should I be worried about case wall thickness variation for range cases? My cases are coming in at .013.
You just want to straighten the case mouth, in 9mm no further crimp is advantageous or desired.

The only possible exception to the above in a rimless caliber is when loading 45 Auto with lead bullets and your gun has a "match chamber". Many semi-custom and custom 1911 builders will tell you to crimp to .469-.469" with the above guns to assure reliable feed.

Otherwise just keep it straight. Brass has more spring than lead. If you crimp the case down into the bullet with a taper crimp die, when you drop the ram and the die comes off the round, the brass springs back slightly, the bullet doesn't. How much you do the foregoing is how much neck tension you have just removed.

That is the way it works.
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