Wow that is odd. My 300RUM don't leave my shoulder bruised after 40 rounds. Not being a smartass, are you taking any new medicines? I have seen where some blood thinners can cause undue bruising. Only reason I ask, is that load ain't that bad. Not like pushing out with H1000. And that ain't that bad out of a 270 with a rubber pad. Especially since you have fired it several times before. Who knows, maybe it was alot warmer outside than usual and you were sweating.

The only round I have that will bruise me is 12Ga 3" slug. 20 rounds of that I am ready for some ice.