I would have a competent gunsmith inspect the bores and certify that they are not corroded through and will still sustain the pressures that a heavy load of blackpowder could generate. That would be money well spent. Thoroughly clean the bores and then shine a bright light down the bore and look for dark regions in the bore. If dark areas are present, these would be warning areas to pay close attention too.
3/4's of an inch diameter would be .75 calibre, the same as a Brown Bess musket. That would make your new/old shotgun an 11 gauge.
Track of the Wolf or
Dixie Gun Works would have the wads and cards that you'll need to develope your hunting and target loads. In my 11 gauge I use a heavy card over the powder, followed by a fibre wad that has been soaked in lube. On top of this goes the shot charge followed by a very thin cardstock or a thin cork wad that goes down over the shot. For this last wad, take a fingernail clipper and nipp the edges in 2 places before use. Those clipps will aloow the trapped air in the bore to escape and not compress. This will make it easier to to ram that last wad down over the shot charge in the bore and keep it from compressing the trapped air and throwing your ram rod out of the bore.
With some of my loads I get better patterns with just the heavy card over the charge and the thin cork wad over the shot. You'll need to see how your gun performs with different charges and wad combinations. THis range work will seem to be a tedious exorcise, but it is time well spent.
I've used my 11 gauge (Brown Bess Carbine) to take everything from doves, rabbits, squirrels to ducks and geese. You are going to have fun with this gun.
-
aim small miss small-
