[Fraschina]

Does anyone offer sabots for reloading in .30 caliber sizes?

If not, would it be that hard to make your own?

 

[Old Grump]

Typical 12 gauge slugs are 50 caliber and 20 gauge are 45 caliber. You would need a pricey collet type of sabot to hold a 30 caliber bullet in place and I suspect the accuracy and performance would be very marginal. Anything is possible but not always advisable.