I've read references to using leather patches, old denim is about the same with even the thinnest leather I have. So I tried to load a .490 out of curiosity but was way too tight.

The remmy balls are the only other balls I have.
I doubt loading a .452 RNFP in a patched sabot would do well in my slow twist (the RNFP is for my 45 colt conversions).