Clusterfrack's 10mm Bearkiller load
Use at your own risk; work up load carefully in each gun!
Test gun: Gen4 Glock 20, 24# ISMI recoil spring, Glockmeister guiderod
Bullet: 200 gr Beartooth lead hard cast gas check
COL: 1.240”
Primer: CCI #300 (non-magnum)
Brass: Starline (virgin brass)
Charge: 9.0gr IMR 800-X (metered in RCBS Chargemaster)
Chrono: average 1209 fps, sd = 8, n = 16
Notes:
Recoil was heavy but controllable. Smoke was surprisingly low, and I didn't notice a big muzzle flash. All brass had mild bulging, dinged rim, ejection dent, flattened primers, and heavier striker channel marks.
This is a followup to some initial load research I did to try to work up a 10mm load for grizzly defense in Montana and Alaska. I had tested this load at COL: 1.260” in a G4 Glock 20 (w/24# recoil spring) and had multiple failure to feed malfunctions when mags were loaded to full capacity. The problem appears to be caused by the wide, square nose of the bullet rubbing against the inside of the magazine. Reducing COL to 1.240" solved this problem, and I've had no further malfunctions.
See the 9mm Outdoor thread for some interesting and useful discussion about handgun use against bears.