Hmmm - I have both sizes, plus .684" which I used in my initial tests in the double barreled smooth rifle. "Smooth Rifle" is the American 'moniker' used to define a smooth bore with both sights & dates back to flintlock days & forward, starting in the early 1800's.

Any of these sized hard cast balls even down to a 16 bore ball of 440gr. driving at only 1,300fps will suffice for such bears at that range. Smokeless loads at 1,500fps have minor recoil & are easily obtained in smoothbores with slightly heavier than Trap loads using powders such as SR4756, SR7625, Herco, Unique, etc. Mathc shot weight to ball weight for starting loads and carry on as if loading for a rifle - small increments at a time. While a chronograph isn't absolutely necessary, it is advisable, particuarly today with them being so innexpensive.

I already have 2 3/4" loads made up with .725's and Herco - just need to get out and test them.

These tests should also include the sabot Lyman bullet which shows good penetration and exceptional accuracy. It measures .68something and fits perfectly in a red WW field wad, WAA12R, I think. In WW metal as mailed tome by friend Karl in Alberta, it weighs 506gr. In pure lead, they are supposed to be 525gr. A .684" pure lead ball weighs 484gr. and in WW weighs 466gr. 1 1/4oz. is 545gr. The WW .725's (mould actually casts .722") weigh 585gr., which is 1 3/8oz.

I suggest, with that size ball, one start with the highest velocity shown with the lowest pressure powder listed in Lyman's shot loads, then raise the powder by 1gr. increments until pressure signs show - extruding primers, excessively flattened primers, sticky extraction, seemingly too-high velocities for short cases. I'd use plastic cases with integral base wads, not cases with inserted base wads, which can be blown from the case and perhaps lodge in the bore. That will form an obstruction for the next shot if not cleared. Same goes for 3" or 3 1/2" loads. The 3 1/2" case can actually obtain over 2,000fps with the Lyman slug in rifled or smoothbores - I expect the recoil might be memorable. I'll stick with 2 3/4" loads, but will make up some 3 1/2" for a friend to test for me - HA! These will be for a Mossy pump with rifled bore. Reports of 2" and less groups with that bullet from a rifled bore (50 yards)

With any smoothbore (muzzleloaders included), it appears the higher the muzzle velocity, the longer the range before they spin off as a curve ball does(trumpet-shaped flight). My own double managed descent groups at 100 meters( 8 to 10" ) showing for deer sized targets, the max shooting range might be 90yards. The Lyman slugs promise slightly better results. I'm quite excited about their testing in both my smooth slug gun and the rifled one as well.

As to the trumpet-shaped flight, I've seen this myself through binocs - really something to witness, the ball headed straight at the target, only to vere off to the side, missing by 2 feet on a 92 yard target. This was a light load in a 20 bore round ball, smooth - with a light, 2 3/8 dram charge - perhaps 900fps to 1,000fps. Everyball doesn't do this, only the odd one, with others impacting just a big low, some high, some to one side or the other, some on-target with perfect flight. Fun to watch when the light is right. High velocity loads seemed to shoot straight with hardly a miss over many shots. This shows a trend not to be dismissed.