Hello, just joined the forum looking some experienced advice. I mistakenly loaded a bunch of 10mm (pistol) and didn't pay close attention to my taper crimp. Consequently, I have a bunch crimped to about .415. I know it should be about .422... These rounds do pass the plunck test in a Glock barrel ( I use a Kimber or Lone wolf while shooting) but very reluctant to shoot these at the range. Also, I have learned that it's best to seat these rounds with the RCBS and then crimp with another die, probably a Lee.
Thanks for your comments
Hello dkuls and welcome to the forum.
Their are several parts to your question so, I'll address each part separately.
Are the rounds in question, safe to shoot?
That will depend on your powder charge. If you loaded them moderately, I would say yes. If you loaded them a grain or two above SAAMI max, I would say pull them.
When to crimp and how much crimp is correct on a straight wall autoloading pistol caliber?
Regardless of caliber, bullet seating and crimping should always be two separate operations. This allows you greater control of over all length and the amount of crimp. (if any)
I always believed the term "taper crimp" is a misleading name because we're not really "crimping" anything. Unlike a roll crimp, on a magnum revolver cartridge, where, rolling the case mouth into a crimp grove will add bullet tension, aiding in powder ignition and keeping the bullets from walking out under recoil.
With straight wall autoloading pistol calibers that headspace on the case mouth, we're not really "crimping" anything as much as removing the flair on the case mouth enough for the round to properly chamber. Adding excessive taper crimp will cause the bullet to distort and the case to buckle at the bullet base, actually reducing bullet tension. The standard results from this are poor accuracy and barrel fouling.
With straight wall autoloading calibers you should be crimping .001 under the case sized diameter. I'll use my 10mm set up as an example. Case mouths come out of my Lee U sizing die measuring .420 of an inch. I then take the empty, sized, case to my crimp die and adjust it so the case mouth comes out at .419 and lock it.
Brand of dies?
I have Lee, CH-4D and Hornady taper crimp dies and honestly, they all work just fine. The only crimp die I caution people about are the Lee Carbide Factory Crimp dies when loading cast or plated bullets as the carbide resizing ring can and will distort bullets, reducing accuracy.
I still use my Lee U (undersize) sizing die, (originally bought for sizing 40 cal range brass for my USPSA Limited gun) because, with straight wall autoloading calibers, bullet tension is determined by the sizing die and I want all the bullet grip I can get with my 10mm.
Hope this helps.
Jeff
fltbed, has give good info in response to your questions. But dkuls the measurements of 0.4215" - 0.4220" are very good taper measurements at the very edge of the case mouth.
That slight taper adds to better feeding as it reduces snagging as the cartridge is traversing the mag to the chamber.
With cast Bullets that are 0.402" the 0.4220" - 0.4225" can help to not cut and PC or reduce bullet sizes as much.
In addition, Hornady makes a nice standalone taper crimp die
Thank you guys for your quick response. Fltbed thank you for taking time to provide many details.
Dave
I don't over think crimp. I find my longest well used empty, load a dummy round, and set the crimp so that I can't press the bullet back into the case. I have yet to have a shorter case lose the bullet in the case or escape the crimp under recoil in the mag due to a failed crimp.
Redding profile crimp dies have been fabulous in every caliber I have used them on.
Thats another die option for you. I only crimp min enough necessary.
CW
I only crimp enough to smooth out the bell. I don?t understand why die mfrs make dies with a roll crimp for rounds that headspace on the mouth