I-7:
What caliber are you shooting? .44 Mag? In my H&R .444 Marlin barrel I have pushed a few 22 Brinell Hardness 245gr Hard cast bullets from an old supply I got in the '90s from Yellowstone Casting in Billings Mont. [I think they're out of business now] to 2400 FPS avg. over my Oehler 35P with a compressed load of IMR 4198. Accuracy was so-so at 1-1/2 to1-3/4 @ 75yds with the H&R, and 2330+/- out of my .444 Marlin 22" with a lightly reduced load, and 5 fairly good-sized deer never knew what hit 'em. Massive internal damage.
From my 7-1/2" SBH and Redhawk with .44 Spl. cases at 1483FPS avg.with a heavy dose of Blue Dot and at 1445 FPS over a heavy dose of 2400 they were just as accurate and effective, Less damage though. No leading in either barrel. One thing I do with the plain based bullets is insert a plug/wafer cut from a plastic tray over the powder first. The thin black and yellow ones found in grocery stores for meat and veggies are best, but a thin cardboard wafer works well also. They keep the flame front from the bullet's base so the heat doesn't splatter the lead, and for some reason, the plastic plugs are found downrange undamaged. I've picked some up and used them again.
Cast Performance says their bullets are good to 2700 FPS without leading, and I've run their 275gr FNGCs to 2275 avg. in both the Marlin and H&R with no leading.
If you are using a softer BH alloy, say--up to 12-15. you shouldn't get any leading up to about 1600+/- depending on your barrel. Just gotta try 'em and see what happens. I hope I haven't confused you with any of this.
WILL