Sabot slugs?

James we used some 50 Cal in the shotgun just playing around from what I could tell is it didn't have the fps to open up the pedals on the sabote 

I've tried (in my .457 Texan) the blue sabots for 45/.357 and gotten some high velocities but accuracy is erratic.

A flier a foot off at 50 yards and other shots in a cloverleaf. Note that usually my target board is cheap panelling and the bullets pass right through, but one test at a different range, we were shooting 1/2 inch plywood and there were sabots stuck in the holes... So the sabot is not shedding. I think the flyers are from where a petal opens on one side but not all of them?

Also, a few years ago I tried reloading 45ACP with these 45/.357 sabots and they shot terrible. These sabots are for black powder rifles where the velocities are quite a bit higher. Tried loading some in 45-70 and they shot the tightest groups that old Trapdoor had ever shot since I got it as my first rifle 50 years ago.

I would suggest trying a speed belt style sabot 

I bet those blue sabots would work If the petals were scribed deeply near the bottom of the bullet cavity with a quick turn on the lathe. This would create a weak hinge that would the petals to open easily at low velocities.

Here are sabots I make for my Hatsan 130QE mod to a 8mm smooth polished bore with a 7.84 mm choke. They can be loaded with any size shot as long as you don't go over 48 grains. The sabots length varies depending on shot size. My first prototype worked okay but these are a huge improvement. The gun shoots nice at 25+ feet. About my expectations for it.

If any of you would like me to do a tutorial on how to make them I will work on one and post it. Not sure how they would work using a slug.

I tried .30" to .22" sabots some/many years ago with some dismal results.

No matter what i tried i could get no better than 3-3½MOA and that was at MACH 3½ or better (so still problems with seperation!).

If you want to experiment then try .451-.452" handgun bullets with paper patch.

But in all honesty you'd be better of finding a lead bullet (that shoots good in your rifle) with a big hollow point if you want expansion!

Most all modern muzzle loader bullets are intended to launch at almost double the speed of a high power big caliber air gun.