So back to the 1941 Win .303. Fired some of the "black label" stuff. Function was fine, if powder a bit dirty (judging from residue and volume of smoke per shot).

Primers are hard and I think this accounts for some leakage. Leakage is annoying and so the ability to screw on a "shooting". bolt head is handy. CCI #34 primers in a few of the cases (with same powder) sealed right as a drum. Cases themselves are right at .060" on the rim, and the cases were not too blown out.

If one doesn't mind the soot then I'd say swapping primers is the ticket and reuse the original powder. But I have the option of 41 gr. of BLC-2.