If you were willing to spend time and money to experiment for a long enough period of time to be able to gain results????????
In other words, have a LOT of patience??????
A shooter could try the following as a starting point.
You would need to purchase at least 500-1000 each of the following......
1. .50 caliber sabots, perhaps a Crush Rib to start with.
2. .54 caliber unlubricated wool wads. Eastern Maine Shooting Supplies has the best prices here, AFAIK, with their bulk 1000/bag price.
3. 0.510" diameter, Circle Fly, nitro card wads, 0.125" thick, bag/1000, Track of the Wolf, $10.99 (1 bag)
4. 0.510" diameter, Circle Fly, over shot card wads, 0.050" thick, bag/1000, Track of the Wolf, $10.99 (2-3 bags)
5. 0.510" diameter, Circle Fly, vegetable fiber wads, 0.500" thick, bag/500, Track of the Wolf, $10.99 (1 bag). You will want these to experiment with the Sky Chief load. Go to our sister forum, Smoothbores, and there is a sticky that explains the Sky Chief load completely. If you want the results, DO NOT DEVIATE FROM THE RECIPE!!!!
6. A small roll of brown wrapping paper of the same thickness of a brown paper grocery store bag. Measure the thickness. This is to make pre-made shot cartridges, which are also explained over on The Muzzleloading Forum.
The shot cartridge, in conjunction with the sabot, MIGHT, JUST MIGHT allow a shooter to shoot loose shot out of a spiral rifled barrel. It might be worth trying, you would have to decide.
I would start with the following recipe, and work from there.
5/8 ounce of #7 shot
7000 grains/pound
7000 grains ÷ 16 ounces = 437.5 grains
437.5 grains ÷ 8 = 54.6875 grains
54.6875 grains × 5 = 273.4375 grains
Powder charge to be 2/5th of the shot charge to start with.
273.4375 grains ÷ 5 = 54.6875 grains
54.6875 grains × 2 = 109.375 grains
1. 110 grains ffg black powder
2. 0.125" × 0.510" dia. nitro card wad
3. .50 cal. crush rib sabot
4. waxed brown paper shot cartridge, 5/8oz #7 shot
5. 0.050" × 0.510" dia. over shot card wad
1. Place powder charge in barrel.
2. Push nitro card wad into bore w/thumb
3. Push sabot into bore, using custom short starter if necessary, until well below the muzzle.
4. Place bottom of shot cartridge in sabot, tearing off top of cartridge to expose the shot.
5. Place over shot card wad on top of shot column, and firmly ram down onto the powder charge.
Only time spent at a pattern board, accurately counting pellets, could determine whether, or not, shot in a sabot/paper cartridge can be made to work in a rifle barrel.
It would be a real interesting experiment.