Hi everybody, I've been loading the Hunter's Supply 45-275 in my 45 Colt and 45acp for awhile now and asked Larry Gibson if you would pressure test the ACP loads just to see where they were at. I boxed up some primed brass, bullets and load data along with some money for powder and shipped it off. Larry assembled them and ran them through his pressure barrel.
Quickload estimate:
45acp-275, seated to 1.237" in Rem brass with Win LP primers, BlueDot, 7" barrel.
8.7gn - 1035fps, 24kpsi 114% compressed load 9.0gn - 1046fps, 27kpsi 118%
Larry's findings:
Testing was done in a Contender 10" 45 ACP barrel. Ambient temp was 75 degrees with a 15% humidity. All rounds were loaded as per your specifications.
The 8.7 gr Blue Dot load under the 45-275 bullet ran 1047 fps with an ES/SD of 74/20 fps. The psi averaged 24,000 with an ES/SD of 7,800/2,300 psi. The 9.0 gr Blue Dot load under the same bullet ran 1110 fps with an ES/SD of 76/23 fps. The psi averaged 27,300 with an ES/SD of 5,600/2,100 psi. Nothing abnormal was observed in the pressure traces of either load.
So it looks like the 8.7gn load should be safe for 45ACP+P and the 9.0gn load should be safe for .45 Super. I thought it was very interesting that the Quickload predicted pressures were very close to the actual measured pressures.
Larry's velocities were higher than mine, but he used a 10" Contender and my gun is a 7" AMT LongSlide HardBaller. Larry also cautioned that a heavy recoil spring and shock buff be used and to watch for excessive slide velocity, also use sparingly so as to not batter your gun.
I have a heavier spring in my 7" LongSlide and the empties just tumble out at my feet. So I'm assuming that they are safe in my LongSlide, but I don't think I'll shoot them in the Star PD with it's 3.5" barrel and Aluminum frame.