I would add to Dan's last sentence, "in a bore that size".
I would restrict my choices in patch material to 12 ounce or 14 ounce denim for a .715"(545gr. in pure lead). There are some canvases in those weights as well.
These "weights" should run from .025" to .034" in thickness.
Dry patches do not allow successive loading/shots & the barrel must be wiped before it can be shot again.
My buddy has a rifle made by Taylor, that is a .75 cal. For plinking, he uses 100gr. 2F, a 12 ounce denim patch and .735" ball that weighs 600gr. It's a nice shooting rifle.
In hunting camp, 3 of us, myself and 2 English Chaps made a 2 3/4", 5 shot offhand group at a measured 50yards with that rifle.(I/we, were a lot younger) One of the chaps
fired only one shot, while the other and I, 2 shots each. There were the 2 Daves, from the UK, both getting moose with modern rifles. (2005 or 6, I think)
Keith uses 125gr. now for hunting, with that rifle, with a WW alloy ball.(12brinel) At 150gr. and over, the balls exited, no matter the angle shot.
It, like my .69, staggers moose. His staggers them a wee-bit harder with the heavy loads.