Not sure the source of this but its very close to my observations in a couple of 45 colts. My heavy load is 23 grains H110 over a 300 gr BTBWFN for 1250-1275 in my 5.5" Bisley. I've also run 2400 to 20 grains but can't recall the velocity - accuracy with H110 was much better. I also run HS 6 for a plinking load and run it 950 ish. I dig the 45 colt.
The source is Hogdon
I got banned on another web site for a debate that happened on this site. That's a first