My son has a QB78 that was built by Roy @ MountainAir with a .20 cal LW barrel. Gun has always been a tack driver. Last weekend he was trying to install a new muzzle break and without me knowing he was really forcing it onto the barrel without supporting the barrel with his other hand.
When we went to shoot he was about 2-3 inches off in windage at 20 yards and about 2 inches in elevation. Seemed at little random withmore flyers than we have seen before. His barrel band is slightly loose.
So I am wondering what to do in order to set his barrel 'back' if you will. Should I loosen the allen grub screw on top of the reciever and twist or turn barrel then retighten etc... Also how tight should the barrel band bolt be.
I assume once we rest it we'll just need to resight in his scope.
Any help is appreciated.
John, I would loosen the barrel band screw first, then loosen the barrel grub screw. Once loose check to see if the barrel is loose in the receiver. The O-rings should keep it snug. Carefully reset the barrel by turning it slightly. You may be able to eyeball alignment as you reset it. Once in position tighten the grub screw. Last, assuming the barrel band is the original stock plastic version, VERY carefully snug the screw. Use a small screw driver to avoid over tightening it. That screw is thinned in the center to clear the barrel and will snap off VERY easily if over tightened. It just needs to be slightly snug (don't ask me how I know that). Your son probably "tweaked" the barrel when he forced the MB. Hopefully this will make things right again.