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Old September 28, 2007, 11:25 PM   #1
actionflies
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357 Magnum Crimp Question

How much should I crimp my 158gr. LSWC with my Lee FCD?
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Old September 29, 2007, 01:51 PM   #2
Daniel BOON
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well.....

I crimp mine as tight as I can w/o indenting the bullet or lead;
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Old September 29, 2007, 01:59 PM   #3
Linear Thinker
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Since you are shooting lead, probably at medium velocity, heavy crimp is not necessary.
When you approach the max, heavy crimp is vital in magnum cartridges.
Lee FCD is easily adjustable, and in pistol cartridges the amount of taper crimp is easily measurable with a mike or a caliper. For revolvers, the roll-like crimp the FCD produces is not easily measurable.
LT
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Old September 30, 2007, 06:43 AM   #4
WESHOOT2
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what I do

I let the gun tell me.

I, using the superior Redding Profile Crimp dies (I use the LEE FCD for auto-loader cartridges), make test loads with varying crimp (it helps to have a range one step out my shop door).

Let accuracy guide your crimp.
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Old September 30, 2007, 04:27 PM   #5
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At the risk of appearing to be one of the Rush Limburger intelligencia I must ditto WESHOOT's every point.
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Old August 29, 2008, 04:44 AM   #6
sandro.1971
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WSHOOT2, I also have Redding Profile Crimp dies for .357 magnum and .44 magnum cartridges.

Could you try to explain me what the right amount of crimp could be.

Let's say you put a resized case (but not expanded) into the shellolder and run it to the top of the press stroke. Then you screw the profile crimp die into the press until you feel it touch the case. In this position you get no crimp.

How many turns you apply to your die at this point ?

Also do you apply any lube before crimping ?
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Old August 30, 2008, 10:20 AM   #7
WESHOOT2
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I actually test

I let the die touch, twist it a bit, and load.
Then I twist it a bit more, and load.
And so on.....

Between each twist I shoot them to observe accuracy. I monkey around quite a bit; I have more than one die in each chambering.

'Medium' is a good place to start.



I lube nothing.
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Old August 30, 2008, 01:26 PM   #8
sandro.1971
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I'm trying to understand where the Medium is.

I did a search and read some of your posts. If I get it right you suggest to give a crimp that would reduce case diameter, measured just below the mouth, after bullet seating of 0.002 inch.

Could you post some pics of the rounds after the crimp ?

Last edited by sandro.1971; August 30, 2008 at 03:00 PM.
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Old August 30, 2008, 04:14 PM   #9
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In .357 Mag, there are two things we are trying to accomplish with a crimp.

1) Keeping bullets from "jumping" forward under recoil
2) Holding the bullet in place to get a complete powder burn before it heads down range.

If you are using heavy magnum rounds with tremendous blast and recoil, it's time to put a firm roll crimp on those rounds so you get the performance out of your powder and so you don't lock up up the revolver with jumping bullets.

If you aren't using heavy loads, start with minimal crimp and see if you need more.
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Old August 30, 2008, 04:29 PM   #10
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I just use the regular seating die to crimp. I put a resized, non-expanded case in the shellholder, tighten down the die until it touches, then go just a *little* more. (very little more). The mouth of the case (no bullet) is just slightly rolled in. Since the cast bullet is going to swell the case when it's seated, this ends up being a medium crimp and it doesn't overwork the brass. (I'm shooting maximum loads using Blue Dot, Herco, and AA#7 with 158 grain SWC's and RNFP's)
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Old August 30, 2008, 04:32 PM   #11
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It ain't critical.
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Old September 1, 2008, 09:08 AM   #12
WESHOOT2
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what is "critical"?

I am unable to post pictures. Inspect Remington, Winchester, or Federal factory cartridges to observe crimp.

Crimp, IME, is extremely critical if accuracy matters.
I am (all too) aware that many 'reloaders' are only 'in it' for the cheap factor, and are more than satisfied if their 'ammo' goes bang safely.
But actual testing, as I described above, will teach open minds exactly how critical crimp can be.
I mean, I didn't invent this subject; someone taught me to "vary and test".....


I rest my case (oh, killin' myself still....).
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