Barrel length has nothing to do with intrinsic accuracy, only velocity. If I remember right 16" is the optimum length for .22lr and any barrel after that just slows the bullet a little.
Here's the one I just did (my favorite):
VQ trigger innards
My super acurate build.
GM 16" fluted barrel
The top one will shoot 3/8" groups at 50 yds but the bottom one will stack bullets at the same distance. The top one is more reliable and likes more different ammo, it is also threaded for my suppressor.