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9mm crimp question


ProGunGuy
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Crimp enough so that the bullet doesn't push back into the case when you push it against your reloading bench edge.

This is not correct. The crimp is not supposed to hold the bullet in place. It is supposed to be held in place by an interference fit with the case. If you are relying on the crimp to hold the bullet in place, you need to get a smaller (i.d.) sizing die.

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Just for more data, I have found that measured of 0.377 seems to work well in my pistols for the pickup brass I use (Win, R*P and Speer mainly). I tried to run the least amount of crimp and get it to feed well. Larger than 377 and I have had some issues, at least on a Springfield XD.

I have noticed on my reloads the bullet will setback a few thousandths each time I chamber a round. I see the comments about crimp not retaining the bullet, but I have wondered if I need to try slightly more crimp...

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I have noticed on my reloads the bullet will setback a few thousandths each time I chamber a round. I see the comments about crimp not retaining the bullet, but I have wondered if I need to try slightly more crimp...

NO! More crimp can actually lessen the neck tension on a bullet. The only thing that assured me no setback was going to the Udie.
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As stated above, a taper crimp is intended to facilitate feeding. It is basically just to remove the flare from the case mouth. That's it. The proper way to check your die is to get a ball gage and micrometer and measure the i.d. of your sized case. That should be at least .002 smaller than the o.d. of the bullet you're using. That's the only way you can assure against bullet setback. If you crimp the thing enough to accomplish this, it's going to be to the point that it has a negative effect on accuracy.

Edited by ltdmstr
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I have found not enough crimp it don't feed properly. Too much crimp will kill accuracy. The type of bullet, you will have more or less crimp. For example plated bullets I crimp to .375 and FMJ .371. The plated is softer material and the brass gouges the bullet if crimped to hard. Where FMJ can take more crimp without gouging. Then it can also be gun specific to which like what crimp. Last week I was trying some loads, all the same crimp and load. My Glock 17 loved them, my 26 hated the same load. The groups you would not have believed they were the same load.

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As several others have stated, the crimp will NOT keep the bullet from setback. A properly sized case is the only way to assure you will not have setback. The crimp, although relative to bullet diameter, is also dependent on the average thickness of your cases. Measuring a random sample of your cases and doubling the case wall thickness and adding that to bullet diameter gives the MINIMUM taper crimp at the case mouth. You should add about .001-.002 more crimp to insure good feeding and not have the base of the extracting case hang up on the mouth of the next round in the magazine while extracting. Thus, after crimping properly, running a finger over the bullet and case mouth interface should feel rather smooth and not too sharp.

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Crimp until your finger can smoothly go over the case mouth. If there is a rough edge it will get hit by the rim of the case coming out of the chamber and stop, pulling off the extractor. That is all you need...

DougC

thats how i do it..

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I measure my crimp at .377/378 consistantly. I keep reading people crimp at .368-.373 many times. So what is the correct crimp for 9mm?

There is NOT a single number, and therefore there are numerous opinions to take its place.

Taper crimp simply erases the belling (or "flare"). If you agree with that statement, then you must also agree that the perfect TC diameter is simply the bullet diameter + 2 case wall thicknesses. Bullet diameters and case wall thicknesses vary from brand to brand which is why a single number cannot be published.

To derive your TC diameter you can physically measure those numbers, or you can simply seat a new bullet into the mouth of a sized, but un-flared, case. Since the TC is there to erase the flare, it stands to reason that if the flare was never there, then the resulting diameter must be the answer.

This test generally results in a diameter from .375 to .379".

If your bullet is pushing back in the case, then you need to polish the diameter of your expander down by .001" and try again.

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I measure my crimp at .377/378 consistantly. I keep reading people crimp at .368-.373 many times. So what is the correct crimp for 9mm?

There is NOT a single number, and therefore there are numerous opinions to take its place.

Taper crimp simply erases the belling (or "flare"). If you agree with that statement, then you must also agree that the perfect TC diameter is simply the bullet diameter + 2 case wall thicknesses. Bullet diameters and case wall thicknesses vary from brand to brand which is why a single number cannot be published.

To derive your TC diameter you can physically measure those numbers, or you can simply seat a new bullet into the mouth of a sized, but un-flared, case. Since the TC is there to erase the flare, it stands to reason that if the flare was never there, then the resulting diameter must be the answer.

This test generally results in a diameter from .375 to .379".

If your bullet is pushing back in the case, then you need to polish the diameter of your expander down by .001" and try again.

Agree with most of that, but who uses an expander for a pistol cartridge? The way to correct it is with a smaller i.d. sizing die.

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I measure my crimp at .377/378 consistantly. I keep reading people crimp at .368-.373 many times. So what is the correct crimp for 9mm?

There is NOT a single number, and therefore there are numerous opinions to take its place.

Taper crimp simply erases the belling (or "flare"). If you agree with that statement, then you must also agree that the perfect TC diameter is simply the bullet diameter + 2 case wall thicknesses. Bullet diameters and case wall thicknesses vary from brand to brand which is why a single number cannot be published.

To derive your TC diameter you can physically measure those numbers, or you can simply seat a new bullet into the mouth of a sized, but un-flared, case. Since the TC is there to erase the flare, it stands to reason that if the flare was never there, then the resulting diameter must be the answer.

This test generally results in a diameter from .375 to .379".

If your bullet is pushing back in the case, then you need to polish the diameter of your expander down by .001" and try again.

Agree with most of that, but who uses an expander for a pistol cartridge? The way to correct it is with a smaller i.d. sizing die.

The powder funnel on Dillon machines(other than the 1050) is an expander as well. I agree though that shrinking the expander does not do much to fight setback. Before I got my bullet feeder which uses it's own funnel/expander I had whittled my original down to where it barely expanded a 9mm case and I still had setback when using FC cases. Like you say, the Udie is the fix.
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