www.eabco.com in search type in sabots it will come up with different types including 30 cal. back in the day just fooling around played with 35 cal sabots in a 458 win mag case, definitely lighter recoil, we ended up keyholing the bullets used so never really went any further with it, but the idea was sound given better bullets and sabots. one of the biggest problems with old sabots we used was I thought the sabot wouldn't hold the bullet tight enough and sabot spun around the bullet in the barrel, today they do make some tools to seat sabots, in our current world all bets are off especially if a person could make a discarding metal or polymer sabot that came apart when exiting the barrel but has inner means of holding the bullets spin when compressed on the bullet when seating in the case. like milled in sharp lengthwise slot or groove that holds the bullet from spinning, otherwise you are looking at a smoothbore with a discarding sabot with smooth interior built in half's, third's or quarter's that separated when exiting the barrel.
I think it's absolutely doable today, I saw somewhere they had velocities on 22cal in 300Wby sabots, I don't know of any re-loading type chronographs that will go over 5000 fps, even my new little Garmin only goes to 5000 fps (very nice little chronograph by the way, still have my old chronograph) no doubt high end laboratory grade chronographs would be needed. common sense would say try very heavy, med and lighter weight bullets just to see where and if it's stabilizing. you might be able to get away with 2 chronographs at different ranges and calculate back to get a starting velocity, but it better be accurate enough to shoot over the distance chronograph.