if one wishes to duplicate .45 ACP ballistics in a .45 Colt revolver,
one can get .45 Cowboy brass and load per .45 ACP recipes! Sort of what I do...
BUT the OP has asked
"what loading of
blackpowder would it take to create a revolver cartridge
with a performance comparable to the 45 ACP, with a velocity over 800 fps and energy around 350 J?"
A simple question.
data found from various sources on the web.
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.45 ACP: 230 gr FMJ 835 ft/s 356 ft⋅lb
Maximum pressure (SAAMI) 21,000 psi (140 MPa)
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.45 Schofeld: 230 gr Lead 730 ft/s 276 ft⋅lb
250 gr Lead 710 ft/s 283 ft⋅lb
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.45 Colt Maximum pressure (SAAMI) 14,000 psi
From a 7-1/2-inch barrel , BP loads:
35 grains BP 250 gr Lead ~900 + fps
30 grains BP 250 gr Lead ~800 + fps.
28 grains BP 230 gr lead 730-800 fps
your mileage WILL vary depending upon brand , lot, etc.
I have found Swiss to be cleaner and faster than GOEX
and Scheutzen to be right up with Swiss.
I myself would not worry about the difference between 28 gr and 30 gr as long as
the load was consistant and hit to POA. As previously pointed out, Modern .45 Colt cases won't hold as much BP as the old cases.
So, I would find a consistant load that fits in the case, compresses nicely, and use a firm crimp.
A chrony is your friend here!
More important is the right Lube, and enough of it.
a long and interesting discussion can be found here (especially KCSO's posts)
https://www.levergunscommunity.org/viewtopic.php?t=20916yhs
prof marvel