That funky bolt handle was designed to eliminate it's barking your knuckles when fired.... Works pretty well from what I'm told.
I wish I'd bought one in .350RM years ago when I had the chance.
They're handy, well fitting rigs and highly sought after for timber cruising for elk and such.
If it were mine, I doubt it would stay a 6mm. Probably do a rebore to 6.5 or 7 and never look back....