I have done a similar experiment with my Model 71/1876 Mauser, with a badly pitted bore- mostly in the grooves. As this series had a .457" groove diameter (& .437" bore), not .446" and .437" like the 1884 models of the 1871's, I re-chambered mine to take the .450 Alaskan ctg., loaded down, of course.

I loaded up 50 rounds with a light load of H4895 for 1,200fps and a 420gr. RCBS .458" bullet with 320grit compound mixed with bullet lube, in the grease grooves.

50 rounds later, the bore shone very nicely. After that, it shot well and did not lead the bore.