Two things that no one has mentioned are the liner o-rings and barrel nut configuration. Both cause accuracy issues in the Impact's. Those liner o-rings do not stay put upon installation and can result in harmonic whip with the thin liners. Bad whip equals bad accuracy. Ernest told me years ago that he puts a couple rolls of tape on each side of each of the four o-rings so they stay located within the tape channel when sliding the liner in the barrel tube. As far as the barrel nut goes, they fit fairy sloppy over the liner. If there is any play in there when the nut is loose the liner (barrel tip and crown) will shift around (from harmonic whip) each shot. I wrap the end of my barrel liner with a couple wraps of Teflon pipe thread tape before installing the nut to keep the barrel nut perfectly centered at all times, even if it comes a little loose.
A third thing... Check the scope over real well. Airguns have blown the guts out of even the high-end scope manufacturer's prized scopes. A rattling reticle tube will show up with bigger group sizes. To test if it is the scope without removing it, chuck the gun in a good heavy vice on the bench so it has zero movement and shoot those 30 yard groups. Or, if you have a known good scope off another gun, mount that and just shoot it for groups without adjusting it. If the groups get super small the scope is the problem.
