Historically speaking, there have been several different .45 Colt b.p. loadings in boxer primed cases over the years.
.........28 grs., 35 grs., 38 grs., 40 grs.
Awhile back I purchased some U.M.C. headstamped .45 Colt b.p. ammunition. I dissected the cartridges and found that three of them contained the 35 gr charge and the rest, 40 grs. The powder had a polished appearance and screening determined that it was FFG granulation
The 40 gr charges in the SHBP (Solid Head Button Pocket aka balloon head) cases required .20" of compression.
Average velocity in a 7 1/2" barrel was 932 f.p.s.
w44wcf
I’ve dug 35 gr charges of 2fg BP out of 45 Colt case sand I don’t know how it could be done with out damaging the individual granuals.
For me the dug out powder (GOEX) broke up to dust mostly finer than 4 fg, true dust. So I do believe the velocity achieved in the 7 ½ “ barrel loading the dust back into those original cases.
As to the original poster question about duplicating maximum power original 45 Colt loads. I think the problem is trying to determine if there was one original load. I do believe a 40 gr charge was tried by the US Cavlery during initial load development but it was quickly deemed too hard on the Colt SAA and the shooter. So the charge was reduced and changed many times there after. I would say that there was no original load, just a wide variety of loads all tried and some accepted for use by the government.
I load 35 gr of 2 fg GOEX in Starline minimum trim to length brass with CCI 350 mag primers and a cast 20:1 alloy 261 gr bullet with SPG lube. I get a average velocity in an Ruger NV 5.5” barrel of 817 fps.
Just for information using the same components listed above but swapping the BP for 9.0 grs (.2 under max) Hodgdon CFE Pistol got me 1040 fps.
So I think any powder charge 35 grs up to 40 grs could be called your maximum.
I’ve seen a uTube video of 45 Colt 7 ½” SAA chron’’ng 1000 fps for some shots with 40 gr of BP.
Unless you want to duplex a BP load with some smokeless the MV you get with your revolver with what ever charge of BP you use is fixed by the gun it’s self. No 2 guns will launch the same load to the same MV.
So what’s like to load up a S&W X frame 460s&w with 2 fg BP? Should make for a nice big cloud of smoke. Wish I had one of those.