OK, how about a .50 cal. sabot cup AND appropriate 'patching' (inside of cup) to accommodate said ball/round size?
Realizing the 'fit' must be tight, to almost difficult, to ram home for proper transfer of barrel twist upon discharge of powder. My thinking, today was...if I did use this "system"' the 'patches' may slip within the cup; thus failing to impart the needed twist for stabilization and accuracy.
Here's what I believe is needed. Somebody needs to develop interlocking sabot cups, so that we can adjust for seasons without having to, own/buy, multiple barrels or multiple rifles. Not that this a is bad thing.
I, personally, would try to develop this if I had the time or the abiltiy; neither of which I have.
littlekid