What crimp? (.357 S@W magnum.)

[wogpotter]

Fairly new to reloading pistols so I've been using the crimp seater die that came with the set. I now realize I want to get a sepereate crimp die, but which one?

Roll crimp?
Taper crimp?
Factory crimp?

I intend to use it with both Hornady XTP JHP's & plated bullets so I'd like something that is suitable for both as I don't want to buy multiple dies.

[Ozzieman]

Why do you want a separate crimp die?
Roll crimp is the crimp you want to use on revolver cases and you need just enough to hold the bullet in the case. Using the dies you have requires only 3 steps if you seat and crimp at the same time.
Taper crimp dies are the only ones I will use for autos and I do them in 4 steps.

[drail]

Use the seating/crimping die that you have. For best results seat and crimp in separate steps. Back off the crimp setting and adjust the seating stem, seat all of your bullets, then back out the seating stem and adjust the die for a firm roll crimp.

[PawPaw]

I use the Factory Crimp die for my .357s, but I want a stout crimp. When you've had a bullet pulled from the cartridge during recoil that ties up the cylinder you tend to put a little more crimp on the bullet.

[drail]

The crimp is never going to hold the bullet in place by itself. Bullets jump because of insufficient case neck tension. Try this - seat a bullet with no crimp applied and press the round against the edge of your bench really hard. If the bullet moves any at all you have insufficient tension. If your bullets move then pull the expander button/plug out of the expander die and measure it. If it is not 3 or 4 thous. smaller than the bullet you are using it is overexpanding the case. You can turn it down in a drill or drill press until it is under bullet dia. I can load magnum revolver rounds and apply no crimp to them and they will not pull under recoil. The crimp helps a little tiny bit to hold the bullet but without good case neck tension it cannot hold it by itself.

[Walkalong]

For jacketed or cast bullets with a cannelure or crimp groove, buy an extra RCBS seater die and remove the seater plug, or buy a Redding Profile Crimp die.

[joneb]

Mr Walkalong, the High Road must be down again Sorry.

I intend to use it with both Hornady XTP JHP's & plated bullets

The XTP has a strong bullet nose, seat and crimpping in one step works well for me, but my brass is trimmed to consistent length 1.280" For HP bullets with a soft nose I will seat and crimp as separate steps, this will minimize deforming the bullet nose, resulting in variations in load density.
For plated bullets I use a taper crimp die, there is less chance of cutting through the thin plating with this crimp.

Bullets jump because of insufficient case neck tension.

The crimp helps with bullet retention and start pressure, or why would we crimp at all ?
If there is insufficient case neck tension on the bullet, this is a sizing issue or a expander plug issue.

Ps. Old work hardened brass may spring back a bit when sizing causing a loss of tension on the bullet.

[sc928porsche]

Bullets for my 357 and 44 have crimp grooves. I use the roll crimp and seat them heavily into the groove. Neck tension alone will not hold my heavy loads.

[tahoe2]

I always put a heavy roll crimp in my magnum loads. 357 Magnum & 41 Magnum.
I taper crimp autos... 9mm & 40S&W & 45ACP

[Lost Sheep]

I kind of rambled in my first composition (which will be my next post when I clean it up). Here is my condensed advice.

Don't buy anything until you figure out why you are dissatisfied with things as they are.

Please tell us.

Also, what kind of press are you using? Single Stage, Turret, Progressive? Do you process in batches or continuous?

Drail's advice about using the combination seat/crimp in separate operations die is right on. There is no reason you cannot do that to see if you really want the extra dedicated die. If batch processing, this is simple.

Lost Sheep

[Lost Sheep]

Originally Posted by wogpotter

What crimp? (.357 S@W magnum.)
Fairly new to reloading pistols so I've been using the crimp seater die that came with the set. I now realize I want to get a sepereate crimp die, but which one?

Roll crimp?
Taper crimp?
Factory crimp?

I intend to use it with both Hornady XTP JHP's & plated bullets so I'd like something that is suitable for both as I don't want to buy multiple dies.

Taper crimp.

Taper crimps are used on cases that headspace on the case mouth (semi-autos, mostly). A roll crimp does not provide good contact of the case mouth with the headspacing shoulder in the chamber.

You COULD taper crimp for a revolver. In fact, it would be a good idea with plated bullets because they generally don't have a crimping groove.

You NEVER want to roll crimp into a plated bullet because if you cut the plating, bad things can happen.

If you adjust carefully, a die intended for a roll crimp can do an acceptable emulation of a taper crimp. Just don't roll into the sides of the bullet.


Roll crimp

Roll crimps are only used for revolvers or cartridges that headspace on something OTHER than the case mouth (almost always the rim).

There are two things that keep the bullet stationary in the case (until firing). The crimp is one. The other is friction with the case walls. The tighter the case walls grip the bullet, the more certainly the bullet is held, and this friction provides greater force than crimp (I am told).

This bullet tension is important not only to keep the bullet in place during handling and recoil of other cartridge's going off, but to provide that the pressure buildup upon ignition follows a good, consistent pressure-time relationship.

So, here's the deal.

When you bell the case mouth, you allow for insertion of the bullet, but no more, lest you have a loose fit. When you seat the bullet, you are pressing the bullet into the neck of the cartridge against the friction of the case mouth and the sides of the bullet. The more the better, generally. When the powder ignites and pressure builds up, the case mouth is expanded by the pressure and lets the bullet go, but only after a proper amount of pressure is present for good combustion. Too little friction and the bullet moves too soon and poor combustion results.

The roll crimp is pretty much just insurance and a little extra retention force if you have really heavy loads. "Gilding the lily" so to speak.


Factory Crimp

Factory Crimp? What's a Factory Crimp? Lee calls one of their dies a Factory Crimp Die (FCD), but their naming conventions leave a lot to be desired. But you should be aware that Lee's FCD performs two functions. It crimps (roll crimp for revolver cartridges and taper crimp for semi-auto cartridges unless you specifically ask Lee Precision for something different). The other function is to size the finished cartridge to ensure it is within SAAMI specifications. This sometimes causes problems because of squishing the lead bullet down in size, loosening the friction grip the case neck has on the bullet.

Lost Sheep

[wogpotter]

OK, in order asked.
I'm going to look into a seperatge crimp die of some kind because the factory seat/crimp die isn't working for me.
It will be used in a progressive press.
It will be used for both JHPs & plated bullets.

The taper crimp for plated bullets was suggested so I figgured I'd ask. I know that revolvers normally use a roll crimp, but which takes preference roll for revolver or taper for plated?

So I repeat, what type do you suggest assuming I've decided this is the route I want to take I just don't know which of the available options is best for my purposes.

[Salmoneye]

Another vote for seating and crimping in separate operations...

Whether that is done as stages in a progressive, or done resetting the same die in a single stage, do them as separate steps...

[wogpotter]

Another vote for seating and crimping in separate operations...

I've already decided that, its HOW I achieve the result that works best with both plated & jacketed rounds I'm trying to decide, nor IF I want to do it seperately.

[mikld]

You can taper crimp both bullets you mentioned. For bullets with a cannalure or crimp groove I like roll crimps, but for plated I don't want to damage the bullet so I taper crimp only. For a 357 Mag. a taper crimp may not be sufficient, so it's a tough call (some powders burn better with "back presure" from a solid roll crimp, and a taper may not keep the bullet from moving at magnum recoil). I use a Redding Prifile Crimp on my revolver (.44 Mag.) ammo but haven't tried them on my 45 or 9mm. IMO, a Lee factory crimp die is a solution for problems best addressed elsewhere; correct die adjustments...

[drail]

Just acheive firm neck tension and use a medium roll crimp on your revolver rounds and a taper crimp on your semi auto rounds. The least amount of flare and crimp will allow your cases to last much longer. Avoid Remington UMC brass. It's so thin they should make special die sets for it.

[m&p45acp10+1]

The Lee FCD will roll crimp revolver rounds. I use one to load up over 200 rounds every week. I set my seating die to remove most of the flare from the case. I use the FCD to apply the roll crimp. Note it is possible to over crimp with one. I did it when doing the initial set up of my die to see exactly what the maximum amount of crimp I could get without ruining the round was. I do not use anywhere near the max amount of crimp due to the fact that I do not need it in .357 Mag. Now I do crimp as much as I can get away with for my .41 Mag loads with slow powders. It helps to get a consistent velocity, and my groups shrank by half when I did this.

To explain:

Taper crimping is just removing the flare of the case to where the round will chamber.

Roll crimping rolls the lip of the brass into a cannulure or grove to give a little extra hold to the bullet. It helps slower burning magnum powders to build pressure as has been stated. It also helps to keep the recoil of the gun from acting like a kinetic bullet puller on the rest of the chambered rounds.

[buck460XVR]

I seat and crimp all .357 in one step on a SS press. Over the years I have alternated back and forth from one step to two and never saw a measurable difference in accuracy or velocities. I use a roll crimp die for both plated and jacketed but adjust the die when crimping plated so it does not "roll" the crimp, just takes the flare out. With the powders and pressures appropriate for plated bullets, neck tension is enough to keep bullets from jumping under recoil. When using slow burning powders for legitimate magnum performance with jacketed bullets, neck tension is not enough to prevent bullet jump and thus a firm roll crimp into the cannelure is needed. This also assists in getting consistent burn with hard to ignite ball powders like H110/W296. While some cases like the .460 need to be crimped in a separate step because the long cases as susceptible to buckling when applying the heavy crimp needed, all my other handgun caliber loads are seated and crimped in one step. This is for revolver and pistols. Like all things to do with reloading, what works for one doesn't always work for another.

[Lost Sheep]

Thanks for answering my questions, wogpotter.

On your progressive press, if you have enough die stations, you lose nothing by using the separate crimping die. The Lee FCD should not be necessary for plated or jacketed rounds, as they are rarely oversized enough to bulge the case and make chambering difficult. So, a spare seat/crimp die with the seating stem removed would as a "crimping die" just about as well as any manufacturer's dedicated crimping die (e.g. Redding's excellent profile crimp die) or Lee's FCD with or without the post-sizing ring removed.

drail and buck460XVR are exactly right about the bullet pull forces for plated bullets. Plated bullets are not driven to the power levels that jacketed bullets can be, nor normally used with the powders that require the high "start" pressures like H110.

Note that since you want a taper crimp on your plated bullets and as buck460XVR suggested you can get taper crimp with a roll crimping die. But you MUST have it finely adjusted. For that fine an adjustment, all your cartridge cases MUST be the same length. So case trimming will probably be necessary. Fortunately, it won't be necessary very often.

I should, at this point, tell you that if you have the combination seat/crimp die's installation adjusted properly (this is not as easy as adjusting two separate dies, but really, not all that hard) you really do not need to separate the operations. But since you have decided to go with the dedicated dies, I will say no more about it.

As mikld mentioned, you can taper crimp revolver rounds with no worries, particularly for non-magnum power levels. If you happen to want a roll crimp on bullets with no crimp cannelure/groove, it is possible, by seating the bullet deeply enough, to roll a crimp over the bullet's ogive. IF YOU DO THIS, you will probably be reducing the overall length of the cartridge under suggested limits for the .357 Magnum. This puts you into uncharted territory. But since you are loading .357 Magnum cartridges, you can consult 38 Special load data to decide if you are inviting dangerous pressures.

Originally Posted by m&p45acp10+1

Taper crimping is just removing the flare of the case to where the round will chamber.

And, for cartridges that headspace on the case mouth, leaving the mouth able to butt up against the headspacing shoulder at the end of the chamber.

Originally Posted by m&p45acp10+1

Roll crimping rolls the lip of the brass into a cannulure or grove to give a little extra hold to the bullet. It helps slower burning magnum powders to build pressure as has been stated. It also helps to keep the recoil of the gun from acting like a kinetic bullet puller on the rest of the chambered rounds.

Well put.

So, short answer:

If you are willing to trim your occasionally to ensure they are all the same length, a single roll crimping die will do for both the jacketed and the plated bullets. If you don't mind having an extra die, using the taper crimp die for plated and low to medium power jacketed loading and the roll crimp die for jacketed high-power loading. I don't know how difficult it will be to find a taper crimp die for .357 cartridges. Most will be roll crimp. I believe Lee Precision will make one for you, though, reasonably priced.

Using the Lee FCD vs any other manufacturer's crimp die or even making your own (roll crimp die) by taking the seating stem out of a combination seat/crimp die is likely to make no difference. Finding a combination seat/crimp die for a revolver round that gives a taper crimp is unlikely.

Lost Sheep

[wogpotter]

Thanks for the response, its exactly what I was looking for.
I've used the RCBS seat/crimp die & as you say it's not that hard to adjust. I was figuring I'd beable to independantly adjust for the 2 types of bullet by having a dedicated crimp die & only adjusting the seating, if it was needed for the 2 bullet types.

Lee makes a big deal out of not needing to trim with their crimp system, so if it works as advertised that would be a help as well. For some reason every case I have is short already so I don't want to trim even more just to get a single length.

[joneb]

. For some reason every case I have is short already so I don't want to trim even more just to get a single length.

If you want a consistent crimp the brass will need to be the same length.
With budget 357 mag ammo I find case variations of .010" after sizing. As an example if the case lengths vary from 1.278" to 1.288" I trim it all to 1.280" this Hornady's recommended trim length, Vithavuori's trim to length is 1.283".

[wogpotter]

If you want a consistent crimp the brass will need to be the same length.

Not according to Lee, thats one reason the Lee die looked so attractive. From the blurb for the Lee FCD:

"Crimps the bullet in place more firmly than any other toolIt is impossible to buckle the case as with regular roll crimp dies. Trim length is not critical."

[wogpotter]

While I was doing some more research on this a different option showed up. What do you think of this:

I have 2 resizing dies in .38spl/.357mag. One is steel RCBS, but i ended up with so many plated cases I bought a Dillon carbide one to upgrade the setup. (It also has the bevelled mouth which makes reloading better on the Dillon press.) So I have this "spare" resizing die.

I read somewhere that you can use this die with the expander stem removed & the die backed off quite a bit to effectively "partial resize" the first part of the case for about 1/8" or so, effectively creating a taper crimping die!

My concerns were resizing a bullet, (not happening the interior diameter is bugger than any .357 bullet all the way to the top of the recess).

Pushing the bullet deeper into the case, posibly causing higher pressures, (also not happening as the bullet contacts nothing at al with the die backed off enough to only resize the 1/8" desired.

Not having enough die nside the press's threads to allign & so on, (don't think its going to be a problem, especially with the extra thich top end of the Dillon.)

So what do you think? Worth a test drive with a small run, or did I miss something & fall for an internet ex-spurt?

[Lost Sheep]

Try it. I am not quite sure what you are intending to accomplish, but a run of one (no primer, no powder) cartridge should give you something to experiment with.

You might wind up reaming out the mouth of the steel sizing die to make the sizing exactly right to not over-compress the case mouth and bullet. Then, I expect you would have a really neat taper crimp die for your .357 revolver.

What benefit that gives you is open to speculation. My first guess is that the "working" of the case mouth would be reduced and your cases might last longer.

Lost Sheep

[joneb]

There is enough adjustment in some 9x19 seat/crimp dies to use it as a taper crimp die for 38spl/357 mag. just remove the seating stem.