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Crimp Question


vossman

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Question for those more experienced than I. Is this too much crimp? I ask because of the ring on the bullet after I pulled it.

I looked through the forums and found several posts saying crimp should be about .420 at the case mouth and that is what this measured at. I have had zero problems with this round in my M&P Pro or Compact other than I think accuracy should be better past 15yds. Rounds are all over the place, even off a rest.

Bullet is .40 cal 165 grn Rainier HP, OAL 1.120, 4.8 grns of W231 and cleaned range brass.

post-35622-0-42669000-1325597430_thumb.j

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My formula is simple.

Diameter of the bullet + 2(thickness of the case wall) - .0005 = diameter of finished round at mouth.

You want to eliminate the belling, and just a tiny fraction more. The bullet is retained by casewall tension, and sometimes helped by the coke bottle sizing effect of many dies. Crimp in most semi auto pistols isn't really needed.

The bigger problem in my opinion is excessive crimping. While true jacketed bullets may not be hurt by it, the same isn't always true with plated bullets. The crimp can weaken or cut the plating. The plating begins to shed on leaving the muzzle. What could well be a decent printing load turns into a shotgun pattern

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To me they look like clean holes, just not anything I would call a grouping like I can get at 10-12yds. I don't think they are tumbling though.

It took 8-10 good whacks with the puller to get this one to release so I probably should ease the die out a bit. I guess it can't hurt to experiment either.

Edited by vossman
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Yeah those are way overcrimped.

Do you have a case gauge? My link

As someone said you just want to get rid of the bell from the expander die. Nothing more. After adjustments I also check to make sure there is no bullet setback by measuring OAL and then pushing the nose of the bullet against my reloading bench. Then I measure again. If it's the same length then that sucker isn't going anywhere. I'd back it off a bit, check to make sure there is no setback, case gauge them, and you should be good to go.

When I pull a plated bullet it looks new. There is no line from the crimp at all. If there is a line, you have too much crimp.

Edited by Babaganoosh
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Crimp is not the first place I look for accuracy.

Plated bullets are not the first place I look for accuracy.

How many factory bullets use the thin-plated bullets?

How many Bullseye shooters use the thin-plated bullets?

I get sub-1" groups at 25 yds with most of my guns off a rest and I don't "measure" crimp. I concentrate on aiming and not jerking the trigger.

What groups do you get with factory ammo?

What groups are you looking to achieve?

You can use factory ammo to set the same crimp for your loads.

Some guns need a lot of crimp and some need none.

Some guns hate certain bullets and powders and other gun love them.s

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Crimp is not the first place I look for accuracy.

Plated bullets are not the first place I look for accuracy.

How many factory bullets use the thin-plated bullets?

How many Bullseye shooters use the thin-plated bullets?

I get sub-1" groups at 25 yds with most of my guns off a rest and I don't "measure" crimp. I concentrate on aiming and not jerking the trigger.

What groups do you get with factory ammo?

What groups are you looking to achieve?

You can use factory ammo to set the same crimp for your loads.

Some guns need a lot of crimp and some need none.

Some guns hate certain bullets and powders and other gun love them.s

Wow, more questions than I thought. I found Rainiers fairly cheap so I bought 1000 to start reloading with. I have 3000 Zero 146 grn HP that just came in the mail today so will reload those once I finish these. Maybe the thicker copper jacket will help and I will definitely tone the crimp down a bit. Will shoot current ammo first and see how it does. I will post pics tomorrow of how it shot.

Thanks for the help folks, I am learning a lot.

V

Edited by vossman
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I have been taught to do what Babaganoosh does. I don't measure the crimp on my rounds at all. As long as it fits in the case gauge and survives being pushed on the reloading bench, it's got the right amount of crimp. Just turn the crimp die in small increments and make sure to tighten the locknut everytime as well.

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I have been taught to do what Babaganoosh does. I don't measure the crimp on my rounds at all. As long as it fits in the case gauge and survives being pushed on the reloading bench, it's got the right amount of crimp. Just turn the crimp die in small increments and make sure to tighten the locknut everytime as well.

Ditto to this...sort of. :closedeyes:

A very wise GM recently told me the perfect crimp leaves a hair like line around the bullet when pulled....and I mean a "hair". I checked some of my new loads (for a new gun) and found my crimp was a little too much, doing as I always have above.

I backed it off a little and saw an increase in accuracy. :surprise:

Good luck!

Steve

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So here is the best group I could do using ammo loaded to the specs in the first post. 10 shots on a 5 inch square, 6.75 inches was the distance between the 2 farthest. Not sure if I should expect more from the M&P Pro (4.25).

I forgot to bring my WWB ammo to see if there was a difference. Any thoughts?

V

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