Hoo, Boy! I sure thought I had more info on this than I found...
Anyway, Dean Grennell started it with some Detonics .451 Mag brass and hot loads, then the project was taken over by Ace Hindemann(?) of ? Texas, who, as I recall, did a rework on the 1911 frame so there was support all around for the brass. He made it more like a '35 Hi-Power frame and linkage. Add a heavier recoil and firing pin spring, and he was purportedly getting about 1300 fps with a 185 gr. JHP.
The big problem with hot-rodding the 1911, of course, is that little half-moon of unsupported brass at the feed ramp. With new brass, a 22# recoil spring, and speer's 200 gr JHP "flying ashtray" it is possible, with an injudicious charge of Blue Dot to achieve over 1100 fps... The brass is NOT reusable, and I DO NOT recommend any experimentation along these lines! The probability of damage to firearms and body parts is altogether too high.
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Shoot carefully... swifter...