Thread: A conundrum

Hello grandpa Mac the casts are .380 and the bore slugged .375 land to groove. The alloy is admittedly a bit of a lottery, 3 parts lead 1 part wheel weight with tin added at 5% by total weight. It works fine for all my other casting including round balls.
4227 is recommended in an old Lyman manual i sort of use as a bible. It also has the universal cast bullet load of 10 grains of unique. I may try that along with some BP.
In case nothing works I may have to resort to your last suggestion of the earmuffs and possibly play a recording of a 105 howitzer beside me.