The reluctance to talk about the 45 Colt’s top end comes from the guns. In Colt SAAs or clones, a 250@900 is the max. S&W’s go a bit faster. As you’ve found, stock Rugers do 1,400. Hamilton Bowen, David Clements, John Linebaugh, and some others build 5-shot 45 Colts that will go 100 fps beyond that, but the only way to get this data is to buy one of their guns. Ruger-only loads will destroy a SAA or clone, and a 5-shot load could wreck a Ruger. Nobody wants to talk about this because they’re worried that some clown will think his SAA clone is stronger than it is and launch his gun into orbit, killing or hurting others. That’s a good stance.
But there’s more to it than velocity. The hot-rodded 45 Colt really does its best with cast slugs over 300 grains. These bullets are not for SAAs, but a stock Ruger will move a 325 at 1,250 fps. (See Hodgdon’s 26th Data Manual.) This load shoots surprisingly flat and it just pounds things, including your gun hand. I once owned two 5-shot guns by David Clements; they pushed a 325 to nearly 1,500 fps in a 7.5” barrel. After a couple of years, I got sick of the recoil. I sold the guns and went back to a 250-grain 44 at 1,000 fps. I ever need that much gun again, I’ll pack a 416 Rigby instead.
There is a ton of good information on the "Writings" page at
http://www.johnlinebaugh.net/. PM me if you have questions.
Good luck,
Okie John