They're a bomb proof looking action, very nice. Would love to see one in a Rock Solid Chassis. I reckon it'd be the Bees Knees. Not keen on the new bolt knob though, I prefer the ball/round knob. Nice rifle.
I think something worthwhile might be a side by side comparison of as identical as possible rifles/load combinations with different barrel lengths. It seems to be a question asked a lot. "How much velocity will I lose", or "How much extra MOA/Mil will I need to get to xxx range" etc. if I chop...
Cut the .260 and let me know how it goes. If it's the .260 I'm thinking of it's not yours anyway so YOU have nothing to lose. :D Mine is at 22" now too.
If it were me? I'd sell the scope you have and put all your saved funds and proceeds from selling your current scope into a new scope. I don't see a chassis or DBM as an necessity/improvement for a hunting rifle.
As for other powders to try. I'd give Hodgdon Hybrid 100V a go. I have recently...