not sure about a 16 1/4.. but Ive got an 18.5" thats getting extremely good accuracy with winchester white box magnums and winchester cowboy 44 specials..
I see a lot of people having a difficult time getting accuracy out of their .44's regardless of bbl length... others seem to have no problem at all..
Im one of the people that got extremely lucky.. I bought a used barrel here, slapped it on one of my frames, went to gander mountain and bought a couple of boxes of ammo, and went to the range.. the only "work" I had to do to it was to slip an O ring onto the stud and float the foreend, which is standard practice for me with all of my single shots these days (to include my non-handi)..
Im getting sub MOA out of mine out to 100 yards..