Tell me why my OAL lengthens going through the crimp dye..... ??

Fasterthanu

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I'll start with two questions:
-Why do my OAL's vary far more than I expect? I would like to see them vary only a few thousandths. Am I asking too much?
I understand that mixed brass will give less reliable seating depths and I have come to terms with that, but today I wanted to load some Nosler competition grade hollow points and noticed something that leads to my next question...
-Why does my perfectly seated bullet (1.125) become (1.135-1.140) after going through the crimp dye?

My setup:
9mm and .45acp
Dillon 650 with Dillon Dyes
Mixed headstamp brass, tumbled with still pin media.

~Fasterthanyou
 
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Fasterthanu

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Ah.. It is a separate die. I noticed this problem after seating the bullet in station 4, and measuring the length (1.125), advancing to station 5 for the crimp die and measuring again (1.135)
 

RVTECH

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Odd that they would be getting longer but anything is possible.

Have you tried measuring the seated rounds BEFORE crimping to see if there was any change? This would narrow down when the lengthening is taking place.

Also how heavy are you crimping the rounds?
 
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Fasterthanu

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Odd that they would be getting longer but anything is possible.

Have you tried measuring the seated rounds BEFORE crimping to see if there was any change? This would narrow down when the lengthening is taking place.

Also how heavy are you crimping the rounds?

Yes, I measured before and after going through the crimp die. It gets longer.

My "crimp" is set light by my perspective. Just enough to straighten the case. I end up with just enough pressure on the bullet to hold it and leave a barely perceptible mark on the bullet.
 

Reno

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Tag me interested!

Only thing I can think of, and this is a stretch, is that the bullet is being swaged by the crimp die?

Otherwise I’ve got no clue? I seat and crimp separately too on a progressive and have never had this happen.
 

Reno

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Another thought, the crimp grabs the bullet on the down stroke pulling it some?

Just random thoughts. I don’t see how crimping can elongate anything. At least in my train of thinking.

How much is your belling die set? Are you widening the case so much that there is little to no resistance seating a bullet?
 
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Fasterthanu

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Another thought, the crimp grabs the bullet on the down stroke pulling it some?

Just random thoughts. I don’t see how crimping can elongate anything. At least in my train of thinking.

How much is your belling die set? Are you widening the case so much that there is little to no resistance seating a bullet?
I would say that there is resistance seating the bullet. I am belling the case just enough that the bullet will sit on top without falling off (it often sits at an angle). I'll try to take a picture and upload here.
 

Reno

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I would say that there is resistance seating the bullet. I am belling the case just enough that the bullet will sit on top without falling off (it often sits at an angle). I'll try to take a picture and upload here.
Thinking about it more, I don’t think that really would cause anything. My thoughts were that if they belling was overdone, and a bullet practically drops in, that when crimping it could allow the bullet to squeeze out. Then I idiotically remembered that crimping dies don’t work from the bottom up, the crimp from the top.
 
We're talking 0.01" as having suspected yet measurable influence on POI on target? Have you measured a sample of factory rounds to determine their range of compliance with given spec?
 
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Fasterthanu

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I checked OAL on a box of HST and it seems it's normal to vary +/_ .07 or more. I may be letting my OCD get the better of me on that. I read on another forum one reloader describing his willingness to allow a variance of anything in the thousandths. If he wanted 1.125, he would accept anything from 1.120-1.130. Would any of you take issue with that rule of thumb? I still cannot explain the crimp die elongating the OAL. I reset everything and it's not happening now.
 
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