Hmmm...I sold a 1905 Bisley 38-40 earlier this year...
Still have two left; a 1903 4 3/4" Bisley and a 1901 4 3/4" SA, both 38 WCF.
Here's some data from my logs-
4 3/4" Bisley-
700-X, 6.7 grs. 189 gr. Big Lube RNFP- 850 fps
700-X, 6.0 grs. 192 gr. RNFP (from an RCBS 40-180 mould)- 739 fps
Clays, 5.5 grs. " " " " " " - 676 fps
Herco, 8.0 grs. " " " " " " - 921 fps
Power Pistol, 8.0 grs. " " " " " - 849 fps
4 3/4" Colt SA-
Herco, 9.0 grs. 192 gr. RNFP (from an RCBS 40-180 mould)- 964 fps
700-X, 6.0 grs. 192 gr. RNFP (from an RCBS 40-180 mould)- 806 fps
Clays, 5.5 grs. " " " " " " - 750 fps
Herco, 8.0 grs. " " " " " " - 850 fps
Power Pistol, 8.0 grs. " " " " " - 871 fps
Power Pistol, 8.0 grs. 177 gr. RNFP (Lyman 40143 mould) - 880 fps
For light loads, in this cartridge as well as my .44 Specials, 44-40 and 45 Colt, 700-X and Red Dot are really hard to beat.
For heavier loads Unique, Power Pistol and Herco are just about perfect, and honestly can be used almost interchangeably so long as you're not loading maximum loads. . I use them in my ancient 1873 Winchester 38-40's with wonderful accuracy, all the way out to 200 yds.
Trail Boss, nah...IMHO it is to the powder world what transfer bars are to the single action world.
CHT