Brownbear, if I were going to paper patch either of my Sharps I'd get in touch with Shiloh and/or C. Sharps. For my 2 cents worth they have more and better info than the other retail outlets and several different paper patch molds for the various calibers.
There's a fella in Sand Point, Idaho....ummm...Buffalo Arms is his company. I can't recall his name but he is VERY knowledgeable about all the old Sharps, Ballard ( he shoots a Ballard, a 45-2.6....I can remember that but not his name!!!) and Rolling blocks. DAVE GULLO!!!!! There...I remembered it. Anyway, he helped me immensely with the working up of loads for my 43 Mauser double rifle. I'd give Dave a call.
I've never worked with any of the 50's except for my 500 BPE double. It has Henry rifling and to make it work good with black I really should paper patch the bullets.....but I just can't make myself do it.....yet. Maybe when our house is finished and I have my loading stuff set up again I will. I have some Hawk bullets for it and they shoot exceedingly well with almost any powder you put under them.
The biggest problem I've encountered with shooting the larger capacity black powder cartridges is keeping the fouling soft, and I've tried everything. Grease cookies, different lubes, homemade concoctions and some other things I can't remember....I just haven't stumbled on the right combination yet. My best results with my 45-2.6 so far is a mildly duplexed load. I think 5 grs. of SR 4759 under a forgotten amount of GOEX Ctg., a Walters vegetable fibre wad and Lymans 457125 bullet. It at least gives me 2-2 1/2 in. groups at 100 yds. I've never fired it farther than 100 yds. so maybe that's a better load than I think it is.
The 500 BPE case is about the same capacity as the 50-140, what's your recipe for good BP loads in it? I ask that and I really would like to know....but I'm convinced it's a function of the Henry rifling in my Double. Others have had the same dilemma until paper patching the bullets.
I can't tell you a thing about penetration on a moose or elk with either of my Sharps but I can tell you that my 45-2.4 and my 40-2.5 Sharps will both shoot lengthways, brisket thru ham, on fairly good sized whitetails....and a very large mulie buck. I've yet to recover a bullet from anything I've killed with them, and that includes some 250+ hogs.....yup...bullets may still be going as far as I know!...hehehe. I've not taken any game with my 45-2.6 and that cartridge is in a Ballard.
Welp...dunno if I helped you any but I do like talking Sharps.....and Ballards....and double rifles.....black powder guns in general!!!!
Vic