I got an ancient (1920's vintage) Spanish Mauser in 7x57 last fall for a pittance. I wanted the action for a project, but I figured I would see how it shot before tackling the rebarreling job. I tried some jacketed loads last fall and was hard pressed to find one that would pieplate rested at 100yds. I was not impressed. But, there was a 140gr &mm Lee mould for cheap, so I figured I'd try that and play with some milsurp powders. Got to the range yesterday with 4895 loads and set up at 50yds. Printed a 1" 5shot with 29gr, one of the best groups I have shot in an old milsurp rifle.
So today I went back with the same rifle and loads of WC860 and I set another record! 10shots in 38". Worst group ever fired in any rifle I have ever loaded for in 35+yrs of handloading. They were keyholing all over the place, some hitting the target perfectly sideways.
Looking for someone who shoots 50BMG and might be interested in the rest of the 860 jug. Live and learn.