Mid case crimp

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Guy B. Meredith

New member
When adjusting either my Hornady or RCBS combination seating/crimp dies my setting often comes down to the setting just short of producing a sag/crimp/bend in the case midway. This is below the bulge at the bottom of the bullet and above the characteristic bulge from case resizing. Unless minimized, the case is destroyed, bent too far to use.

I load .38 spl. and .357 magnum exclusively.

I assume that this comes about because the seating portion of the die is still pushing when the crimp is too tight for the bullet to be traveling into the case, the case takes the pressure and collapses. Is there any way to increase crimp and still avoid this short of separate dies?

Guy
 
L

labgrade

Member In Memoriam
"I assume that this comes about because the seating portion of the die is still pushing when the crimp is too tight for the bullet to be traveling into the case, the case takes the pressure and collapses. Is there any way to increase crimp and still avoid this short of separate dies?"

Sounds like you've diagnosed it correctly - but too, moreso sounds like you're trying to crimp too hard. You can still over-crimp by doing a single bullet seat & then a crimp (& although never having used the factory crimp die, I can't imagine that it could "repair" a case that's been over-crimped).

Very few .38 special loads require all that much of a crimp. & only a few of the most stout .357 will require anything close to what you seem to be getting. Your case collapse is more than likely due to way too hard a crimp. If you can fire off a full cylinder of loads & the bullets (especially the last = #5 or 6 in the cylinder) aren't backing out at all, then you're OK for a crimp for that load).

Although it's probally best to seat & crimp in different "stations/operations," I did the seat/crimp ops at the same time for close to 40 years on a single-stage press with zip for "badness." ;)

Set your die first to seat & then dial it in to crimp (ask questions if still having a prob here) - & that only enough to hold the bullet under recoil for that load.

Even though I never have for .38/.357 loads (except for the most accurates) trimming cases always is a good idea to ensure a consistant crimp.
 
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Mal H

Staff
I agree with labgrade's good answers. It does sound like you're attempting to crimp too much. However, another thing to check might be where you're crimping on the bullet. Are you crimping into a cannelure or into the wall of the bullet? If not into a cannelure, then even a not-so-tight crimp can cause what you are experiencing.

Apparently one thing labgrade and I do differently is that I set up the crimp distance first and then the seating depth. If you set the seating depth first and then lower the die to crimp, the seating is now off. No matter which way you do it, it's a trial and error type of thing. And don't worry too much about the errors during setup, that is, where the crimps aren't perfect or the seating depth isn't exactly right. The cartridges are all shootable for practice rounds.
 
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TheEggman

New member
I set the seating depth (OAL) first. Then I back the seater out a few turns and get the crimp just right. With the newly crimped and seated cart in the press, raise the ram and lower the seater until it's snug against the bullet tip.

I recently had a friend at a machine shop cut me a set of 1/4" dia steel rods, the exact OAL of my favorite/frequent loads and grind a round nose on one end. These little 'Guages" are prefect for quickly setting the (OAL) without trial and error. (Mostly error)

Best

Egg
0 <-- His Mark
 
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Guy B. Meredith

New member
I set the seat first, seat bullets in several cases, back off the seater, set crimp on the cases/bullets then bring the seater back down to the correct position.

I am using West Coast Bullet copper plated bullets with canulure, but sometimes I am able to crimp hard enough to cut the plating and other time the crimp (roll) does not even leave a mark.

I may go back to taper. I have been able to crimp with taper hard enought to disfigure the bullet then back off.

I want to experiment to see whether a firmer crimp will give more consistent burning/velocity.
 
B

bfoster

New member
Guy,

It sounds as if your cases vary in length. It just isn't possible to get a servicably consistent roll crimp if the brass varies more than a couple thousandths in length.

I have tried to seat and crimp in the same operation using, as you appear to be using, the procedure outlined by RCBS. I've never been able to produce the quality of ammunition this way that I can produce by seperating the seat and crimp operations.

Further, the RCBS sizing and expanding dies for revolver cartridges I've owned tend to work the brass in such a way as to make the case crushing scenario you describe much more likely than do the dies of Dillon or Redding. I'll go into why I think RCBS makes dies this way if you like...

Bob
 
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