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How Much Crimp?


Icefire
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Well found out the hard way that I wasn't really crimping my ammo (new reloader)..

Jam after jam after jam... 1 out of 5-7 rounds, stovepipe, double feed, failure to go in battery.

How much should I crimp? I just made some test and I wounder which way should I go? I got a CZ75b, Lee pro 1000, 1.135" AOL. I don't want to buy the Factory crimp since I would have to crimp them one by one after.

Left is my ammo before, next is rim just taper enought to remove the belling, next to are taper crimper more.

Crimp is : .417 .413 .398 .398, wall is .417

thanks

crimp.jpg

Edited by Icefire
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Holly Crap! Your taper crimp should look like the 2nd from the left. The others look like your going to blow something up. My general rule for crimping is to measure the case wall multiply by 2 then add your bullet dia. My 40 crimps are aroundt .420 The only reasons you need to crimp is keep the bullet from pushing back when it hits the feed ramp and to keep the edge of the case from dragging when doing the same.

Your problems sound to be more with the gun than ammo. Shoot factory ammo and see what she does then if it works try loading to that ammo's specs.

Disclaimer: Try all the about at your own risk.

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Well those were minor load, probably 130-140pf (4.2gr Universal Clay, 180gr plated).

I have a 14lbs spring in the gun vs the 16lbs factory.

The wall thickness in mid height is .416-.417 so getting .420 would be asking for trouble no?

Those were just a test, to see what crimp I could be getting with my lee pro 1000. I too find the second round a bit better than the first, and the last one feel really smooth (no edge praticly). But the last to are ROLL crimp, not taper crimp like the first two.

Edited by Icefire
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The wall thickness in mid height is .416-.417 so getting .420 would be asking for trouble no?

Those were just a test, to see what crimp I could be getting with my lee pro 1000. I too find the second round a bit better than the first, and the last one feel really smooth (no edge praticly). But the last to are ROLL crimp, not taper crimp like the first two.

The wall thickness should be around 0.010" maybe a little more or less. Again understanding the meaning of why we need crimp try 0.420" and if your can squeeze it by hand and push the bullet back go a little tighter. Once you get where you want it pull the bullet and see if you crimped so thight that it left a ring around the bullet and if so loosen it up just a little.

Also a forum search might will show you something we have missed.

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About halfway between #1 and #2 should be about right.

You really should not crimp more than what it takes to just flatten the case mouth back against the bullet. The round on the left looks to almost be right. The second from the left looks like it has too much" crimp on it. The ones on the right are crimped dangerously tight!

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I agree with George ..... and notice George does not spit out a number for a crimp. Look at the crimped round, stop when you see a burnished edge reflecting in the light. That is all you need. Forget trying to get to a certain number. HHjr.

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notice George does not spit out a number for a crimp. Look at the crimped round, stop when you see a burnished edge reflecting in the light. That is all you need. Forget trying to get to a certain number

Abso-Frickin'-Luteley. There is NO SUCH THING as a magic crimp number for any round. Brass thickness, bullet diameter and amount of case mouth flare all contribute to this being a variable, NOT a constant. Derive it by trial and error for YOUR brass, bullet, case flare combo. You can measure bullet and brass thickness, then add the bullet diameter to twice the brass thickness and test to see IF that is OK, but that typically winds up being a starting point for a dynamic adjustment that is finalized by eye, feel and testing. That is all!

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From Lee Precision:

Dummy cartridge #2 would be the correct crimp (counting from the left). The two on the right look like the bullet seating die is adjusted too far down, and the case mouth is actually passing through the crimp shoulder, while the one on the far left has no crimp at all.

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I sent both the pic and mesurement..

I agree with George ..... and notice George does not spit out a number for a crimp. Look at the crimped round, stop when you see a burnished edge reflecting in the light. That is all you need. Forget trying to get to a certain number. HHjr.

That exactly it according to Lee as the 2nd round in my pic.

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Here's my procedure. Measure the OAL with a caliper. Put the nose of the finished round against the reloading bench, put your thumb behind it and lean into pretty hard. Then measure it again. Keep tightening up the crimp till the round doesnt shrink any under heavy thumb pressure. That leaves it as tight as it needs to be to avoid being set back if a round gets rechambered, without driving up pressure or degrading accuracy.

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A quick, easy way - take a round of factory ammo that works reliably in your gun, back your crimp die off a good bit, run the round of factory ammo all the way up and screw the crimp die down until it firmly touches the factory round. Use that as a starting point. Mine are .420.

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