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  #1  
Old 03-20-2017, 3:51 PM
Erik16 Erik16 is online now
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Default .357 Magnum Crimp and Bullet Movement

I just started reloading .357 and I am working on a few load developments. I am using a Lee factory crimp die. With the ram all the way up, I turn the crimp die until I make contact with the bullet. Then I do an additional of a turn or 1 full turn and seem to get the same results. I load the revolver and shoot 5 shots and then I re-measure the 6th to see if I get any bullet movement. Here is what I get..

Before and After
1.577 – 1.584 = 0.007
1.574 – 1.579 = 0.005
1.578 – 1.580 = 0.002
1.574 – 1.579 = 0.005

Is this normal for .357 Magnum to get a small amount of movement?

This is the load..

New Starline Brass
Win 296 – 15.5 to 16.4gr
CCI Small Pistol Magnum
COAL 1.575
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Old 03-20-2017, 4:00 PM
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That would work for me. Honestly, I just put a good crimp the revolver ammo, and have never had an issue in twenty-odd years. If I'm within a couple thou of the spec, I call it good.
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Old 03-20-2017, 6:29 PM
hambam105 hambam105 is offline
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Plated bullets, right? How did I know?

Measure you bullet length before seating. Remember...the bullet, not the cartridge...tell us what you have.
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Old 03-20-2017, 7:10 PM
Erik16 Erik16 is online now
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Nope, using Nosler jacketed 158 grain bullets.
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Old 03-21-2017, 11:07 AM
hambam105 hambam105 is offline
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Good.

There is a difference between cylinders with most revolvers. Some cylinders are holding the cartridges tighter than others.

Check velocities as well. But I really wouldn't worry it me too much. I've successfully reloaded a couple thousand full pressure .357 mags and this has never been a concern for me or anyone eles I know.
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Old 03-21-2017, 8:16 PM
Whiterabbit Whiterabbit is offline
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Works for me. I assume .007 jump is far away from OAL = cylinder length?
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Old 03-21-2017, 10:06 PM
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Might be half that due to measuring error...so what is a shooter to do? Shoot!
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Old 03-21-2017, 10:51 PM
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So final die sets bullet depth and crimp.

Unscrew the seating guide, turn the die a bit more into the loader and increase the crimp.

How does the crimp appear visually?
Forcing brass into the bullet is too much...

Roll crimp or taper crimp die?
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Old 03-21-2017, 11:58 PM
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Quote:
Before and After
1.577 1.584 = 0.007
1.574 1.579 = 0.005
1.578 1.580 = 0.002
1.574 1.579 = 0.005

Is this normal for .357 Magnum to get a small amount of movement?

This is the load..

New Starline Brass
Win 296 15.5 to 16.4gr
CCI Small Pistol Magnum
COAL 1.575
Comments as to perspective. Some things in reloading. A "few thousandths" make big differences. Other things a "few thousandths" make no difference. OAL on pistol cartridges is one of the latter.

Now to your numbers..... Largest movement you had was only .007". For perspective, that is a little less than twice the thickness of an average human hair. Even using a Ransom Rest, you would never be able to discern any difference in accuracy with that tiny difference in OAL. Especially from a revolver, with its many inherent variables that you have no control over. Like variances in different chamber alignments with barrel/cylinder. And cylinder gap.

If you are loading to the 16.4 gr charge, that is close to max for Win-296 and a 158 gr jacketed bullet. I would be surprised if you didn't have a small measurable amount of bullet slip after 5 rounds with a load that stout.

That's the long answer, with explanation attached.

Short answer.............You're GTG............Choot Em.
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