Would love to see a picture of that one. Were the irons replaced to the new barrel or did it have any to begin with?
Seems like a Swift AF in 286 would be a good choice (if they could be found) as would a Barnes TSX in 250 grain or a TTSX in 286. Am thinking your 20" might get 2,300 fps headed out the tube. Would be good medicine for most that walks on four legs methinks....
bhtr