Yukon Gold
Wish I could help with this, I just picked up my Katahdin 209x50 barrel today. A friend has one also, seems to like 75 grs. T777 with power belt, unknown grain. I just wish I could have gotten the barrel in stainless steel to match my frame.
I won't get to shoot mine untill the weekend of CHRISTmas, let us know how you do and what works for you.
CASHEP