Tom's right, Martin - with round balls and cupped gas-check wads upsidedown, I've achieved some realistic big game grouping at 100 meters. With iron sights, shooting offhand with 2 lefts and 2 rights I've managed all 4 on an 8" to 10" plate at 100 meters. This, from a double smoothbore. My buddies ask me for more of the .684" balls about every other year for their duck guns. They pack round ball loads in case a moose or deer comes down for a drink. They've got both birds and a freezer full of red meat on the same trip more than once. They use the same loads for the round balls as for ducks, only use a thin t-shirt patch as if for a muzzleloader.

I use a wad column consisting of a cup gas check cut off a used trap wad over the powder, then fiber or card wads necessary to fill the case to another gas-check cur off a trap wad, sitting cup-up. The ball sits in this and I fold crimp over the ball.

Lyman has data listing wad columns they've worked up using a .690" ball. Putting the base gas check wad cup-up centres the ball as it travels down the tube. Failure to do this will greatly increase group sizes. A .690" ball will just pass through a full choke in a 12 bore and that's the reason Lyman uses it.

Lyman also sells a mould that casts a short waisted slug that fits inside a 12 gauge cup and is supposed to give good accuracy. The slugs weigh 506g.r in WW metal and about 525gr. in pure lead. They call it a sabot mould as the field shooting plastic wad is the sabot. this wasted slug inside the shot cup might shoot well from a comercial rifled barrel. The twist is about right.