I just put together my old tower pistol my neighbor gave me as a kid. I found out that to my surprise it is not a .58 but a .69!
Now the only load data I could find for any similar pistol was for a .58 1855 pistol carbine, which Speer said would be safe with 40 grains of FFg. I figured, being a much larger bore, that about 45 grains would be safe. So far, I am right. I don't see any problems arising from the few shots I've taken so far. The only loads I have shot out of it so far are buckshot loads. I use 45 grains of Pyrodex RS, (Just to get rid of it), a wadded up cut square of paper, a cotton ball with Bore Butter worked in, then six 00 buck pellets, another small wad of paper over the shot. It may seem a little odd having a "wad of paper" as part of a load, but they are really just taking the place of overpowde and overshot cards. The lubed cotton ball acts sort of like a wad. Over all it seems to work pretty well. The recoil is very light, but this big pistol sure speaks with authority.
I have a question for any of you avid flint shooters out there though. It seems like after a few shots my flint gets really chipped and short, so that I have to re position it to get a spark again. Also, after about 20 or so shots it is too busted up to work at all. Is my mainspring too strong (I worked on it a little), are my flints crappy, am I positioning them wrong, or am I getting about the standard life out of them?