A problem with comparing 445 SuperMag loads to 45 Colt loads is that the 45 Colt has three loading levels and you have to clarify which level you are talking about. Nominally, the 445 has the same maximum operating prssure as the 44 magnum. (Not that every body and his brother doesn't push it harder.) 44 magnum pressures fall into level III for the 45 Colt. The Ruger Blackhawk is famous for taking hot 45 Colt loads but it takes only level II loads. There are very few guns out there that are really suitable for level III 45 Colt loads. You can run them i na 454 casull but then you have a 454 casull revolver, not a 45 Colt revolver.
Bullet weight for bullet weight and pressure for pressue the 45 Colt will crank up more velocity than a 44 Magnum simply because of the bigger bore providing more bullet base area for the pressure to work on. But the 445's longer case and flatter pressure curve gives it an edge here. The bullet weight for bullet weight the 445 should match or exceed level III 45 Colt velocities.
Be aware that a large part of the 445's intended purpose was to push heavier than standard bullets, not simply to achieve hyper velocities. So you can expect 200 fps over the 44 Magnum but that 200 fps might come with the next heavier bullet as well. With the same weight bullet I'd expect closer to 300 fps over the 44 Magnum (assuming at least six inches of barrel) if both loads are going over the same chrono and you ignore the numbers in the factory blurb sheet.
