For those of us engaged in developing loads for 45 LC and 454, try to include some Hodgdon Lil'gun in your testing. In rimmed pistol cases over 15 grs water capacity, it duplicates H110/W296 velocities and much lower pressure in bbls 7 inches and longer. For example the 454 Cassull, 7.5 inch bbl, a 260 JHP does 1900 fps at 54,000 CUP with H110, and 37,000 CUP with Lil'gun (Hodgdon 2002).
For the 45 LC, 7.25 inch bbl, Hodgdon lists 1410 fps for a 250 gr XTP at 29,800 CUP (Lil'gun 25.5 grs). I forget what the CUP spec is for different lever guns in 45LC, but there may be a fair amount of room to grow here, particularly in the 20" bbls.
As bbl length grows, Lil'gun will actually exceed H110/W296 veocities at safe pressures.
If you really want to go FAST, I am developing Sabot loads for my 454 Casull using Knight high pressure .451 sabots and a full range of .40 caliber bullets. I am reluctant to provide data here yet, as there are a few details to work out. Lets just say that I am certain that this approach will yeild more than 2000 fps with a 155 gr Gold Dot in a 20 inch bbl using 45 Colt brass at moderate pressures.