Author Topic: problem crimping 357 magnum  (Read 683 times)

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mikefamig

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problem crimping 357 magnum
« on: January 13, 2021, 10:35:06 pm »
I startedreloading about six months ago when I inherited a Star press and some loading supplies. I cleaned up the press, set it up for 38 special and all went well. I've loaded a few hundred rounds and fired a few and it all looks good.

tonight I started to set the press for loading 357 magnum ammo. Everything was fine until I got to crimp and set stage. I used the same procedure that I used with the 38 special. I brought the crimp die down until it touched the top of a flared casing. Then  I set the bullet press to get the OAL approximately correct. Then i slowly worked the crimp down to get a nice snug crimp and then the bullet press to the desired OAL (~1.560 - 1.570).

The problem is that the walls of the brass casing is buckling a little bit when O press the final stage. I set and reset and approached the crimp slowly and gently and still I see a little wrinkle in the wall of the casing. Is this OK?

TIA, Mike.

mikefamig

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Re: problem crimping 357 magnum
« Reply #1 on: January 13, 2021, 11:03:28 pm »
Here's a pic that shows the crimp and the rings around the body of the casing where it buckled a little.

NYKenn

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Re: problem crimping 357 magnum
« Reply #2 on: January 14, 2021, 07:18:39 am »
No, I do not think it is okay. It may function, but it also stresses the case and could lead to premature case failure.

Have you confirmed this is occurring at the seater die and not another stage.

Perhaps the case is being impacted at the powder drop and being slightly compressed by the spout when the head is brought down?  Possible also on the priming station but less likely.

Definitely let us know when you work it out and find the cause.

NYKenn
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mikefamig

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Re: problem crimping 357 magnum
« Reply #3 on: January 14, 2021, 09:09:11 am »
Yes I am certain that it's happening in teh last stage when crimping. I increased the flare to allow the bullet to enter the casing with less resistance and it is no better so it is the crimping that causes it. Today I'll try backing off the crimp a little  (~1/8 turn)  at a time.

I also had some trouble setting up this stage with the 38 special. Moving the crimp die effects the OAL more than I would expect it to. The crimp die seems to be hitting the bullet and pushing it down.

Can anyone give me detailed instructions on setting the combined roll crimp and bullet press stage?
« Last Edit: January 14, 2021, 09:29:04 am by mikefamig »

rbwillnj

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Re: problem crimping 357 magnum
« Reply #4 on: January 14, 2021, 09:57:32 am »
When I set up machines for a roll crimp, I back of the seating stem so it doesn't come into play.  I put an sized, unflared case in the seating/roll crimp station, and with the tool head as low as it goes (not camed over) bring the die down to where the crimp section of the die just touches the mouth of the case.  Then bring the die down another half turn.  Then I adjust the seating stem to get the desired OAL.   You will mess up a few bullets in the process, but that's jus the way it is.   If you happen to have a loaded round with the correct OAL, you can put that in the seating station and with the tool head in it's lowest position, bring the seating stem down to where it stops on the bullet.   This will get you pretty close but you might need to make some minor adjustments.

The condition you have happens when the crimped portion of the brass bottoms out in the crimp groove, or digs into the bullet while the bullet is still moving.  The brass has nowhere else to go so it begins to buckle or bulge the case below the bullet.

This is also a common problem with bullets that have no crimp groove like 45 ACP.   If people try to crimp too much they get a bulge below the bullet.  Doing a Taper Crimp in a separate station alleviates the problem.   For 45 ACP, I set the Seating/Role Crimp die so it removes the flair, but doesn't crimp, then crimp with a Taper crimp die.
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mikefamig

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Re: problem crimping 357 magnum
« Reply #5 on: January 14, 2021, 10:32:49 am »
Thanks much, I'll work with it some more today and let you know how it goes.

Mike.

mikefamig

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Re: problem crimping 357 magnum
« Reply #6 on: January 14, 2021, 12:09:43 pm »
Thanks much, I'll work with it some more today and let you know how it goes.

Mike.

I had at it again and things went much better.

I started by removing and carefully cleaning the crimp and the seating stem and re-assembling. There was some muddy stuff in the stem and it is all clean now.

Then I placed a sized casing (no flare) in the shell plate and adjusted the crimp die to just touch the case and locked it in position. I  did not turn it down at all as I don't want a crimp yet. The seating stem i raised as high as it could go at this point.

Then I flared the same casing, placed a bullet in it and put it back in the press.

Then lowered the press and brought the seating stem down to just touch the top of a bullet.

Then I repeatedly lowered the press adjusting the seating stem about 1 or two turns at a time until I got the OAL that I want (1.565).

Then lastly I turned the crimping die down about a half turn while raising the seating stem and equal amount.

I'll do a couple more before loading any powder but it looks good. Thanks all for the help

Mike.




mikefamig

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Re: problem crimping 357 magnum
« Reply #7 on: January 14, 2021, 12:19:06 pm »
Something I'd like to add

I noticed that when I pressed the bullet into the casing with no crrimp the bullet fit very tightly. I could not even spin it with my fingers and it was not crimped yet. The 38 special casings that I loaded previous to this were much looser and definitely needed the crimp to hold the bullet in place. I'm thinking that these 357 casings are a harder brass material that the 38's.

Mike.