Sabot petal loss is not an indication of sabot failure. One of my most accurate high end loads always peels off petals. Failed sabots look kinda like a twisted helicopter blades and/or the center is blown out.

My old Accura 45 shot like CR*P with either Harvester because the bore was .452. The MMP worked fine for me in all but the hottest/heaviest bullet loads in a .451 bore. Mine are actually from Hornady but i think they are the same as the MMP tan unless its a different polymer. They look identical.