I have not had any luck with RETUMBO either when shooting 300 smk’s. I have tried the Sierra “accuracy load” which calls for IMR 4350. Was not impressed.

So far my bests 3 shot groups have come from using 80.9 grains of Reloaded 22, WLRM primer, Lapua brass with a C.O.L of 3.740” These groups have measured just at an 1” @ 100 yards. Over the years I have tweaked & tuned loads for several rifles ( some were savages) and eventually they became very good shooters but this beast is taking me to task!

I also want to try REL 25 and VV N570.