The ammo is CCI SV out of my relatively new M41.
I clean the M41 thoroughly after each shoot and also give the ammo a bit of a clean with WD40 to get rid of the wax - all aimed at minimising the chances of ejection failure.
I've also recently swapped my recoil spring to the 6.5lb spring (from Wolf), however this tumbling has been occurring prior to that change as well.
Not all rounds are tumbling but certainly quite a few. Here are a few pic's though there were others that were even more obvious:
and just to show that they don't all tumble:
I clean the M41 thoroughly after each shoot and also give the ammo a bit of a clean with WD40 to get rid of the wax - all aimed at minimising the chances of ejection failure.
I've also recently swapped my recoil spring to the 6.5lb spring (from Wolf), however this tumbling has been occurring prior to that change as well.
Not all rounds are tumbling but certainly quite a few. Here are a few pic's though there were others that were even more obvious:



and just to show that they don't all tumble:
