I too am interested in a lever gun that take handgun rounds. I have two Marlins now, .30-.30 & .45-70. I am not overly thrilled with the .45 colt but my next lever gun will definitely be a hand gun round, just not sure witch one. The main target is paper but if something with a little more mass needs shootin at, I don't want a cartridge that can't handle it. Open to suggestions.
There really is no need for the 45 colt when you have a 45-70. Especially if you reload.
If you aren't reloading I would suggest a marlin in .357 magnum. Those guns can feed/fire both 357 mag and 38 spcl so they will get enough velocity and bullet weight that you could take deer within about 100 yards or so with the 357 mag, and punch paper with cheap 38 spcl.
The 44 mag leverguns unfortunately tend to have a poor rate of twist for most 44 mag rounds, and so they don't tend to be all that accurate.
I have only fired the 454 casull in a revolver, so I really don't know much about it. Though like the 357 mag, you can use both 454 casull in the levergun as well as 45 colt. But having a 45-70 already really makes those two unecessary. (<can't spell that word)
And to anybody who might care, I spent the weekend shooting in wyoming with a friend of mine.
Using my 45-70 with a 350 gr cast lead bullet moving at a chronographed 1278 fps, I was able to repeatedly and accurately hit a 2'x2' steel gong at 800 yards offhand. The bullets hit with authority. It was much easier hitting the gong with my friend's scoped 300 WSM with a 36? power scope. The mirage makes things fun at those ranges.
I also was shooting prairie dogs with the 45-70. Average range on those 20 oz coke bottle sized targets was 125 yards. Iron sights.
Fun weekend.