357 Magnum Crimp

[mjl650]

Loading 357 Mag for a 6” revolver, 125gr XTP, 9gr Unique in Hornady trimmed equally brass. I’m using a Redding profile Crimp die and have tried different settings from a medium to a very heavy crimp(to the point it is difficult to pull the bullet). Measuring the 6th cartridge COL before and after firing the other 5 in the cylinder the COL grows .005”. If I crank down any harder on the Crimp die it starts to deform the cartridge. The growth is consistent in the heavier Crimp settings.
Is .005” acceptable or what am I doing wrong. Hope I explained it right.

 

[AckleymanII]

I do not crimp mine, just use another bullet seater to straighten out the bell on the case mouth. 17.8g of IMR 4227 with 125g sierra, Win, or Rem HP. Crimping destroyed the fine accuracy of this fine 6" GP 100

 

[MikeT124]

You should be OK as long as COL of 1.590" is not exceeded. Unique is an interesting powder choice for that load. The Hornady Manual (10th edition) does not list it and virtually all of the powders listed are somewhat to significantly slower burning powders than Unique. If you got that loading from a source that you consider reliable, I guess you should be OK with it. The Alliant 2019 manual lists the 125gr Speer GDHP with a max chg of 9.6gr Unique, you are not using a Speer case as listed, they also list CCI 500 primer for that load. Form this I would keep an eye on it but most likely OK load. As far as COL growth to be honest I've never been concerned about it, but you have piqued my interest. I'm going to do some testing with both .357 and .44.

Mike

 

[K22]

I'm shooting the same bullet in a S&W Model 586, 6" 357 Magnum revolver.

A roll crimp works extremely well for me. It prevents the bullet moving forward under recoil and provides enough bullet tension to obtain optimum ignition. Speer wrote a paper on this years ago, i.e. the benefits of a roll crimp. For magnum loads, I prefer the roll crimp over the taper crimp. A roll crimp will only work with a bullet that has a cannelure. If it doesn't have a cannelure, then a taper crimp die will be needed to crimp the bullet.

I'm not sure how to explain this so it will be clear but I'll give it a try. You don't want to over do the crimp - it's not necessary and will only over work the case and shorten the life at best, at worse you'll bulge the case. I like to seat and crimp in one step. The following describes how I set up my seating die to accomplish this in one step to achieve the desired amount of crimp.

1. First seat the bullet without a crimp so the top of the case is at the mid point of the cannelure of the bullet.

2. Remove the seating stem and screw the die down so the crimp groove of the die touches the top of the case. You'll be able to feel it.

3. Lower the ram and going in small increments at a time, screw the die down then raise the ram until you feel resistance, i.e. the case being crimped into the cannelure. Visually inspect the cartridge, there should be a gentle roll crimp of the case into the cannelure. The crimp should be smooth. The case lip should not be crushed into the cannelure. When you reach the proper amount of crimp you should be able to see the case lip slightly curved into the cannelure. There should be a smooth transition roll into the cannelure. There should be no bulges in the end of the case. Run your finger over the case - you should not be able to feel the edges of the case at the crimp location, it should be smooth and there should be no distortion of the case body.

4. Once you have the desired crimp set, lock the die into place. Reinstall the seating stem until it contact the bullet and lock it. You now have the seating die set up to seat the bullet at the cannelure and crimp it into place in the same step.

When shooting, check unfired rounds in the cylinder to make sure the bullet has not moved under recoil. If it does, reset the die for a little more crimp.

 

[wagonman]

good bullet tension is more important than you mite think, if its lacking on a heavy revolver load no amount of crimp will help stop bullet creep

 

[Twicepop]

Five thousanths (.005") movement is much, as long as the cannelure doesn't move ahead of the crimp, you probably have nothing to worry about. To get proper uniform crimps on your .357 Mag ammo, your case lengths need to be as consistent as you can make them. I use plus (+) or minus (-) .003" from my target length when loading for it, especially with jacketed bullets that have a shallower cannelure than most cast slugs.

 

[riflewoman]

You want the crimp in the canellure to look like the picture.

 

[Sniper338]

I do not crimp mine, just use another bullet seater to straighten out the bell on the case mouth. 17.8g of IMR 4227 with 125g sierra, Win, or Rem HP. Crimping destroyed the fine accuracy of this fine 6" GP 100

I dont crimp anything I own. Not one straight wall case. Set your dies up right. All you need is the sizer die, bell/flare die, and seater die. You dont have to flare out case mouths much at all. Then set the seater up to seat the bullet and close the case mouth nice and snug.

 

[noylj]

>1. First seat the bullet without a crimp so the top of the case is at the mid point of the cannelure of the bullet.

I prefer to set it just below the top of the cannelure. Also, never found any group size advantage to trimming cases (.38 Spl, .357 Mag, and .44 Mag).

Since the OP has the Redding Profile Crimp Die, there is no reason to set up the seating die for crimping and no advantage to one step seating/crimping.

From 1) I move to the Redding Profile Crimp Die. I adjust the crimp so there is visible curve of case mouth into the cannelure/crimp groove, but not to the point of actually contacting the bullet. You can pull a crimped bullet and inspect for damage and back off until you aren't leaving a crimp ring in the bullet.

Most folks over-crimp—not willing to simply start with a slight roll, fire say 12 rounds and check the last round of every six in the cylinder for any bullet push out.

 

[mjl650]

>1. First seat the bullet without a crimp so the top of the case is at the mid point of the cannelure of the bullet.

I prefer to set it just below the top of the cannelure. Also, never found any group size advantage to trimming cases (.38 Spl, .357 Mag, and .44 Mag).

Since the OP has the Redding Profile Crimp Die, there is no reason to set up the seating die for crimping and no advantage to one step seating/crimping.

From 1) I move to the Redding Profile Crimp Die. I adjust the crimp so there is visible curve of case mouth into the cannelure/crimp groove, but not to the point of actually contacting the bullet. You can pull a crimped bullet and inspect for damage and back off until you aren't leaving a crimp ring in the bullet.

Most folks over-crimp—not willing to simply start with a slight roll, fire say 12 rounds and check the last round of every six in the cylinder for any bullet push out.

Yes I seat and crimp in separate operations. I loaded some bullets this way ^yesterday and am heading to the range on Monday to see what happens.

Thanks to all for your comments and info. Also measured the length of the cylinder on my 28-2 and the bullet would have to grow .050" before it caused any interference issues. The growth was a consistent .005" on the ones I measured on the last range trip and the targets were't any worse than any other time.
I measured this last batch prior to crimping and also after crimping by the above method, the bullets actually shrunk .001/.002".