I bought some 265 grn .452 Cast Performance WFN bullets to load up some heavy 45 Colt loads. My secondary use for the same bullets are to put them in a proper fitting sabot & use them in my 50 cal Knight M-L. There is no reason why they shouldn't work superbly, just a little range testing 1st.
I have even used a home case 44 cal pistol bullet in my M-L that did the job. A WFN hardcast out of a M-L would have to do great. Just compare the FPS out of your M-L to that of a 6" handgun barrel. You could easily be up near 1800 fps, compared to down near 1100 or so. My 120 grn charge of Blackhorn 209 gives a steady 1950fps with a 250 grn SST. That would offer some serious penetration, the WFN opening up a good channel along the way.