A Barnes bullet is probably your very best choice for those velocities. New Easy-Load sabots have taken the Barnes bullet into a very practical hunting projectile. In the old days they were bearcats to load in some rifles. Sounds to me like you've thought this out and have a quite workable solution. I agree that I'd much rather be shooting a high performance muzzleloader than a slug gun if the surrounding area is safe for it and you have shots beyond 150 yards. I've looked at a nice used Savage at my local gun dealer that is priced no higher than conventional inlines and considered it but I really don't need another muzzleloader. Right now I'm using a Knight Revolution loaded with 260 grain Hydro-cons and two Triple 7 Magnum pellets... open sights only for the season. I imagine I'm pretty close to 2,000 fps and the rifle is quite accurate... but I'm limiting my shot attempts to 150 yards with it.