I've got a Rossi 44 mag with a 24 inch barrel, and did have, for years, a Winchester trapper in the same caliber. I've shot mostly cast bullets in both, with no problems. My main go-to powder for both has been 2400. One of the things I'd suggest is to open your lever and look to see if the magazine follower is yellow in color. Those are plastic, and Steve Young (Nate Kiowa Jones) sells a steel replacement for these, as does the Smith Shop, another on-line source. It's a quick, simple job to replace the plastic part, for starters. Steve's DVD on how to slick up a Rossi is well worth having. Over the years, I've found that the RCBS 215 grain SWC gaschecked bullet has been a reliable and pleasant component to shoot out of both of my 44's. Many like heavier bullets, but these have worked just as well for me.