RE: Barrell Length
I shoot the USAK with the 22" barrel and it has not hindered me so far. I am pretty confident with it out to 125yds, maybe 150.
I have been extremely happy with this gun, but I will say that this gun tends to be a little bit picky when it comes to bullet & powder choice. That is most probably a function of both the barrel length & the 1:28" barrel twist working together.
This is not an insurmountable problem since I can now put bullets through the same hole at 100yds - but it took awhile to get it there. If you don't have the time for (or don't enjoy) spending a lot of time at the range working up loads, then I would suggest the 24" barrel, as I believe you will find it a bit more forgiving in the accuracy category.
"Every moving thing that liveth, I give unto you as meat" (Gen 9:3)
Trust God..........but keep your powder dry!