I'd look at 1 3/8 oz shot loads with Blue Dot from the manuals. Pressure generally drops when a solid is replaced for loose shot. Try this link there are a couple of 1 3/8 oz loads using Blue Dot that may be a good place to start.

http://www.alliantpowder.com/reloaders/r...=3&gauge=12

I have a Blue Dot load for my paradox that uses 34 grains of Blue Dot and a .735 gr slug. I get about 1,070 fps a few feet from the muzzle. In a .727 full choke pressure gun it produced about 2 3/4 tons of pressure (safe in a Ball & Shot) but velocity was 1,185 fps. You can look at the old post here:

http://forums.nitroexpress.com/showflat....true#Post170222

If you are sure of the original projectile (and have them) and the gun is in unaltered condition, you should be able to start low and go until the barrels group together. I'm sure you know bore guns cross and shoot low when velocity is too low & will shoot high and apart when overloaded.

Good luck sounds like a fun project. Be safe and get help if you think you need it.

CC