Got a 16" hb with vq hammer and extractor (best mods you can do) and its a tack driver. With jsut basic ammo its accurate as all hell. Cant wait to put some high end ammo in it. I love how compact it is with the 16" barrel yet it feels liek a full sized rifle which the 10/22 and others never felt like to me.
Now just a thought, since you seam to be able to do precession work (the Hatsan choke build you are doing), why not just do a threading job on the 16" barrel. I mean there is a lot of material up there to thread so might be a idea.