If u were using a soft wad behind the bare ball, the ball will be pushed by the wad and an indent forms in the wad around the ball, holding it in more or less one position in the bore. Since the wad s acting as a gas sealer, somewhat, you don't have gases blowing by and moving the ball around in the bore. At the short range of 25 yds., you can expect some reasonable fist-sized groups. You would have to use a ball with a diameter closer to bore diameter, to get better groups sizes at 25 yds., and fist sized groups out at 50 yds.
Remember that you are shooting a "Knuckle" ball, ion Baseball terminology, because the bore likes rifling needed to impart any spin to the bare lead ball. Some members here report getting good accuracy with their bare lead balls, using balls with diameters close to bore size, and then dipping the balls in molten wax, and letting them dry. Some roughen the surface of the bare balls with a coarse file, before dipping the ball in the wax. Some members use softened cushion wads behind the balls, so that the ball indents the center of the wad, and the wads then keeps the balls fairly stable as they move up the bore.
I do believe that you have to have an adequate gas seal(1), and that the velocity has to be lowered by using either a slower burning powder, or less powder(2), to get the best groups using bare balls.
Since you are shooting a projectile that weighs so much, penetration is never an issue deer hunting. Depending on the diameter of the ball chosen in your 12 or 10 gauge guns, the ball will weigh at least one ounce or more! Distances are also short - 50 yards and less. That is 150 feet or less for the ball that is leaving the muzzle at 800 fps, if you back off on the powder charges.
Do the math to calculate time in flight from muzzle to target.
I Know men who hunt deep thickets for deer and take shots at 3 yards and less using shotgun slugs! 25 yds.(75 feet) is considered a very long shot for them. You don't need a load, or gun and ball combination, that shoots 5 shots touching at 50 yds. to kill deer at those short ranges. AND, a .72 caliber ball going 800 fps is going to put a huge hole in both sides of a deer at that close range, too. :hmm: :thumbsup:
