With my recent rifle recoil damage to my right eye, I have been playing around with pistol loads to keep from going nuts...
So I have been playing around with various 10mm Auto loads for the last couple of weeks.
My dies are carbide RCBS 40s&w / 10mm Auto... With a Taper Crimp.
I was seeing all sorts of pressure changes during various trips to the range because it is very hard to always get exactly the same amount of crimp with these dies.
So I marked the outside of the dies with various lines. Then after pouring powder and seating bullets to exactly the same COL... I hand screwed the crimp die die down until to became firm against the case. Then I backed the case out and then tried various rounds with the crimp dies being turned down in 1/4 turn increments .
Bullet: 200 grain Hornady FMJ-FP
Case: Star-Line virgin
Powder: AA#9 13.2 grains.
COL: 1.250 inch
Fired from a Glock 20sf, 20 pound recoil spring and stainless guide rod. Stock 4.7 inch barrel
Temp 20F. 20 knot wind, blowing snow.
0.25 turn crimp = 1,110 fps
0.50 turn crimp = 1,154 fps
0.75 turn crimp = 1,166 fps
1.00 turn crimp = 1,188 fps duplicates original Norma Load in Glock 20
1.25 turn crimp = 1,160 fps
1.50 turn crimp = 1,152 fps
The 1/2 and 3/4 turns gave the best accuracy in previous test. With the 1.0 turn coming in a close 3rd. The heavier crimps caused larger groups and high pressure signs.
I also tried some 155 grain Hornady XTP hollow points:
The brass, primer and COL are all the same.
Only 14.8 grain of AA#9.
0.75 turn crimp = 1,270 fps and a very nice group
1.00 turn crimp = 1,290 fps
1.25 turn crimp = 1,256 fps
1.50 turn crimp = 1,245 fps