I have considered sabots.
Although the use of sabots would definitely increase the possible range of projectile choices, I wonder what kind of saboted projectile would work well at a rifling rate of one in fourty inches.
At this point, the sixteen bore balls are looking like a decent choice for this gun, especially as they were found with it in it's case and having seen what I've seen while looking closely into the chamber and barrel dimensions in light of the ball and cartrige sizes the thing came with.
I wouldn't expect to run this gun at greater ranges than 200 yards. The sights on it just aren't long range sights, the front blade is smallish and wedge shaped, the rear sight is short and the leaves have small notches. I wouldn't run it with telescopic sights or hack it to take any other kind of sights either.
I just want to run it as it is. And it's in absolutely beautiful shape. Not just good shape for a hundred and so-odd decades old either, but really beautiful and clean.
If you know of a ligther bullet type that should give good accuracy in a 1/40 twist barrel, let me know. Zippy performance might just be fun.
I intend to run only black powder in this gun. With chambers this huge and with as many different types of black powder that are available I'll have a fair bit of latitude setting it up with a load that will shoot and regulate properly with the round balls. Running sabots would surely put quite a spin on things and I can imagine getting a load developed that would shoot right would be quite a bit of work.
Still I'd be happy to hear about what's worked for you.