Fire-forming reduced loads for RUM
I have three 300 RUMs, two 338 RUMS and a 375 RUM. Given they burn at 63K PSI the brass can only be reloaded about 3 times. I'd like a reduced load I can use for fire-forming + plinking. My Speer reloading manual (#10, 1977) has reduced loads using SR 4759 (RUM not invented yet) - and the latest Speer manual (#14) is sold out.
I'd like some reduced loads that won't take away one of the 4 lives of the brass. I know that reduced loads don't guaranteed reduced maximum pressure, but I should be able to find a load that can be used for target shooting + fire-froming + not stress the brass.