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Old August 14, 2012, 01:02 AM   #1
three-fifty-seven
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Am I properly crimping my rounds?

Howdy guys,

I am wondering if I am properly crimping my heavy .357 Magnum loads (158gr bullet + 17 grains of Lil'Gun around 1540fps). I am a fairly green reloader and I still am figuring out how much crimp I need to apply. Here are some pictures of my crimp jobs as I just want some validation that I am doing it right. Also I am using a Lee .357 crimper.

Now I know I am using two different bullets (Speer 158 plinker + 158 Hornady XTP) to find an answer but both these rounds have two different crimps.





Thanks.

Last edited by three-fifty-seven; August 14, 2012 at 01:08 AM.
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Old August 14, 2012, 03:16 AM   #2
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the one on the left looks way bit much. the right looks better but i would notch it down just slightly from that.>>>
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Old August 14, 2012, 05:09 AM   #3
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The one on the right is plenty of crimp...

Basically with heavy loads, you need enough crimp to keep the bullet from jumping under recoil, and not enough to deform the bullet or buckle the case...
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Old August 14, 2012, 08:54 AM   #4
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Agree, too much on the left. The right one looks better but hard to tell.
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Old August 14, 2012, 04:30 PM   #5
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Can't see them well enough to tell.

When the inside edge of the case mouth is against the bottom of the cannelure, it's enough. Less than that,n is too little, more may buckle the case and lead to early case failure, cracked mouths.
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Old August 14, 2012, 07:30 PM   #6
three-fifty-seven
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Okay thanks, I just wasn't sure.
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Old August 14, 2012, 08:17 PM   #7
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The pics are tiny, blurry, and worthless.

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Old August 14, 2012, 09:18 PM   #8
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If you click on the pics, they should expand. They're not bad.
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Old August 14, 2012, 09:23 PM   #9
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Maybe a discrepancy between tapa and his pics then. It would be a great app if they fired the devs and put competent ones in their place.

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Old August 14, 2012, 10:22 PM   #10
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Fixed it for ya. Right looks about perfect.
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Old August 14, 2012, 10:59 PM   #11
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As stated the round on the left maybe a bit heavy, the case mouth distortion from over crimping can hinder chambering. But adequate crimp maybe needed to provide enough start pressure for the powder to burn efficiently.
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Old August 15, 2012, 10:33 AM   #12
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I find it easier to get a good roll crimp than it is to photograph them
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Old August 15, 2012, 11:53 AM   #13
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"Step-down" crimp

The crimp on the right seems about right for a jacketed bullet. As somebody has already written, the idea is to turn-in the case mouth until it touches the bottom of the cannelure, but no further.

HOWEVER, with the advent of some of the heavy-recoiling cartridges like the .500 and .460 S&Ws, there has been some rethinking of the crimp so as to keep these revolvers from walking the bullets out of the case mouths and tying up the cylinders. Speer calls these extra-heavy crimps "step-down" crimps, and makes SOME of their bullets with flat-bottomed cannelures to accomodate them. The case on the left has what looks like a step-down crimp.

For a step-down crimp, the idea is to make the case mouth start at the front of the cannelure and lie flat for a short distance in the bottom of the cannelure until it reaches the back, then expand back to the uncrimped case diameter soon enough that the bullet itself is not swaged/distorted by the crimp. That is definitely hard on the case mouths, and will reduce case life by leading to early splitting. And, with some dies that have sharp edges on the crimp ring, it will scratch brass and may scrape-off nickel plating.

So, it is not a good idea to use a step-down crimp unless it is needed to keep the bullets from moving under recoil.

In a .357 Magnum, I would not think that a step-down crimp would be needed, unless perhaps for ammo to be used in one of those new ultra-light guns that is designed for concealment.

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Old August 19, 2012, 02:35 PM   #14
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SL1,

"Step-down crimp" and "step down crimp" searches just lead back to you.
Is there another name?



I have been doing the Lee 308 rifle factory crimp upside down on hard recoiling 32 S&W long cartridges.

I am about to do Lee 458WM rifle factory crimp upside down on hard recoiling 45 auto rim cartridges.

It allows me to make a high recoil crimp at any OAL I choose.
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Old August 20, 2012, 11:32 AM   #15
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Clark,

You got me thinking about the term "step-down crimp" so I pulled-out my copy of Speer Manual #14 and found their discussion on page 751. BUT, they called it a "neckdown crimp". So, maybe my mind messed-up the term, but I THINK that I have seen it called a "step-down crimp" elsewhere. The Speer write-up says
Quote:
"No special or extras equipment is required if you use Gold Dot bullets and RCBS dies. Rather than rolling the case mouth into the groove, neckdown crimping irons a step at the case mouth that nearly fills the cannelure. ..."
Anyway, try searching for "neckdown crimp" and see if something from Speer comes up.

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Old August 22, 2012, 11:10 PM   #16
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Wow did Image Shack go anti gun ?
The main reason I crimp revolver loads is to prevent bullet jump.
Take your calipers to the range, shoot all but the last round in the cylinder. Is the COL the same before and after ? If not you have a problem.
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