My 5.5-22 NF are both 56 my 3.5-15 is a 50.
I'm getting ready to do a 6.5 something. Can't decide on 6.5-284, 6.5-06 or 6.5-06AI but when it's done it will have a NF 5.5-22x56 too.
I had the same decision to do and a friend of mine let me go and run a 100 rounds through his 6.5x284 and that made my dicision. I was using 130g bergers and playing around from 100 to 600 and had alot of fun. I am setting mine up a little different but not much. The recoil is nothing on his and that really helps me. He used a bell and carlson varmit stock and I am going with a HS varmit stock with the palm swells.