How close should case lengths be for roll crimping 9mm?

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TheNatural21

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With prices and available of 9mm going a little crazy I thought I'd try loading my own. I reload rifle cases, just never bothered with 9mm.

I got a Lee 3 die set which comes with a seating die that can also be set up to do a roll crimp at the same time. Instructions say that cases need to be the same length if you're going to do a roll crimp. I checked the length of my cases after sizing and they're .746-.750", is an extreme spread of 4 thou close enough? Or should I pick up one of the taper crimp dies that Lee says are more forgiving with different case lengths?
 
In my experience, I’ve never trimmed 9mm cases. I reload mixed range brass and never bothered measuring them. So I’d say 9mm is not case length sensitive.

9mm needs a taper crimp. Not a roll crimp. A more accurate term is a straight crimp. Yes, it sounds like an oxymoron.

All you want to do is straighten out the “bell” you formed with your powder through die, to facilitate seating the bullet.

Look at new factory 9mm ammo. The casing is straight. There is no visible crimp. You want to accomplish the same with your reloads. Our sizing die already reduced the casing diameter by the correct amount, to provide the necessary tension to hold the bullet in place.

Some folks may disagree and say there has to be a thousandth of an inch, or two, of crimp. That’s ok too. But not necessary, IMO. Straight wall reloads have worked many years for me with no issues.
 
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Your Lee 3 die set for 9mm should have come with a taper crimp die, not a roll crimp. While nothing is impossible, I would say that a roll crimp die with a 9mm set would be close to that.
 
9mm luger is a cartridge that headspaces on the mouth of the case. As such, it should not ever be roll crimped. It should be taper crimped, to eliminate the flare made by the mouth expanding die. Most seating dies will also crimp, if adjusted properly.

As to length, since it is a straight wall case, there is very little elongation from resizing and I have never found it necessary to trim to length.
 
Roll crimping is generally for rimmed cases (38 special, 357 etc). Cases that head space on the mouth (9mm, 45 acp ,etc) are generally taper crimped.

Your 9mm die set will almost certainly be giving you a taper crimp. Most people don't bother trimming straight walled cases.
 
Thanks guys. I went and checked my die set and it contains a carbide sizing die, an expander die that also allows powder through, and a seating die that the instructions definitely say can also do a roll crimp. The paperwork with the die set suggests getting a Lee taper crimp die to avoid the need to have cases trimmed to the same length. I also found this online, from Lee's marketing material:

"Taper crimp dies are used to correct the problems caused by the improper expanding plug design or adjustment. They distort the bullet shank and reduce accuracy. Because the Lee Expander flares the minimum amount, consistent with easy bullet insertion, all of the flare is removed with the bullet seating die, thus eliminating the need for a taper crimp die. 3-die set."

Might just load some up with no crimp of any kind and see how it goes.
 
I suggest you load them up with your die set as a taper crimp die, as I suspect you have a generic set of instructions. As always, make a dummy cartridge without primer or powder, and see what happens with the crimp and seating in your barrel; before you make up a bunch of live rounds.
There is a difference between removing the flare, and taper crimp. Perhaps a bit more reading in your loading manual on the difference and how to see if you have properly taper crimped.
 
As Al-sway says make up a dummy cartridge. Put the pointy end against the edge of the table and see how much force is need to push the bullet back into the case.

Also do the 'plunk' test. Remove your pistols barrel and drop the round into the chamber. It should go 'plunk' as it drops freely in all the way and not a tight 'scrape' in fit.
 
Thanks for the tips. I'll make up a couple dummies and see how it goes. Might review the pistol section of one of my reloading manuals too - that's probably a better idea than piecing together info from marketing materials.

Edit: you guys were right of course. My seater die does a taper crimp. Instructions must just be the same as the revolver dies. Not sure why that threw me off so much, but I'm back on track.
 
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Thanks guys. I borrowed some projectiles to make some dummies while I wait for mine to come. I know seating depth will change with different bullets (as beautifully illustrated above), but now I know the equipment and process. I was overthinking it for sure.
 
You will flare the case mouth slightly to make it easy to insert the bullet without scraping it when it is seated.

First adjust the seating die down so that it hits an empty case. This the depth at which it will start to crimp. Back the die off a rev, so it will not crimp.

Now adjust the seater stem so that the bullet is seated, say at 1.120". Seat a few bullets.

Now back the seater up a few revs, and adjust the die body down so it touches the case mouth. Now turn it another 1/8 of a rev. and crimp some of those seated bullet cases. You want just enough of a kiss to take off any hint of flare.

If you like the crimp, lock the die body in that position, and then screw the seater stem down to touch the bullet, and lock it.

Now the die will seat and crimp perfectly. Slight variation is case length won't matter.

Pull your barrel and use the chamber as a gauge to make sure all of your first 25 loads will chamber and plunk properly.
 
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