I load .45 Colt for my New Vaquero and an 1873 Winchester clone. I use a lot of Herco powder. 9 grains under one of my hard cast 240 grain truncated cone bullets. The Herco fills a lot of space in the .45 Colt case. Runs around 850 fps out of the 5.5" Vaquero and 975 fps out of the lever gun. Very accurate out of both. Recoil is easily managed in the Ruger and very mild in the big Winchester.
Excellent advice to use a moderate burn rate powder with high bulk to best fill the large .45 Colt case for accuracy, low recoil, and ignition reliability.
Herco is a large grained powder manufactured by Alliant (the company formerly called Hercules).
The name of the powder is obviously a self-reference from before they rebranded the company itself.
I'm unsure how widely available it is off the shelf in brick and mortar locations.
A look around online isn't promising.
Graf's, MidwayUSA, Midsouth Shooter's Supply, Natchezz, and even Powder Valley don't have it in stock.
Strange...