Winchester 45 Colt brass seals quite well in my experience. But even so, the 73 design, which only exposes the lifter block to fouling, works very well with BP. Avoid SASSLite loads, keep the lifter block lubed, use thinner/annealed brass. Like the revolvers, I only tear down once a year or so, lubing with Ballistol and cleaning with water. Unless you can anneal it, avoid Starline brass in the BP 45 Colt.
You should be using soft .454 bullets with large lube capacity. Larger diameter will aid in chamber sealing, and the lube not only keeps the foulling soft, but helps to expand the case with hydraulic pressure as the softer bullet compresses on ignition/initial acceleration.