I just thought I'd update this with some data which I've now actually tested/used:
***WARNIN
As always, work up and look for signs of overpressure before attempting to use max. data someone else has posted. What works in one persons gun, might not work in yours (and could explode in your hand - ouch!).***
My MAXIMUM load!!
Pistol: Ruger KP345 (4.2" barrel) with Wolff 17# recoil spring.
Bullets: Hornady 200gr XTP
Brass: *Never Fired* Starline - 45 SUPER
Primers: Winchester LP
Powder: Hodgdon LONGSHOT
Charge: 10.2gr
COL: 30.2mm
I didn't have a chronograph, but these loads are definitely cracking past the sound barrier (I think the bullets started going supersonic at 9.6gr - so, a guess would be 1200'ish ft/sec from my short barrel). If it's breaking 600ft/lbs of energy at the muzzle I am happy (my goal).
Note: 10.2gr of Hodgdon Longshot was my pistols max/reliable load. The brass and gun could have gone higher, but due to magazine spring and physics I had 1 round out of 8 flip vertical in the magazine due to the excessive recoil @ 10.4gr.
At 10.6gr every shot flipped the next round vertical in the magazine due to the awesome recoil.
Very fun load!!
My Regular 45 SUPER load:
Pistol: Ruger KP345 (4.2" barrel) with Wolff 17# recoil spring.
Bullets: Hornady 200gr XTP
Brass: Starline - 45 SUPER
Primers: Winchester LP
Powder: Hodgdon LONGSHOT
Charge: 8.6gr
COL: 30.2mm
Very accurate and fun because it's got a little more "pop" than .45ACP - It's 45 Super
