I switched the barrel from my 308 to a new one from criterion. At the same time, I changed the scope base to a 20 moa weaver mount. The farthest back screw will not engage the threads in the reciever. I left that screw out and remounted my vx2 4-12 that was on it previously (there was about six months between taking it off and putting it back on). The rings were never removed from the scope. I thought three screws would be enough to at least get it in the neighborhood as far as sighting it in (and let's be honest I just wanted to see what it could do). My first two shots went into the same hole about a foot left of where I wanted them. I adjusted the scope but after about six inches of movement to the right it stopped adjusting even though I could still hear and feel the clicks. I went through an entire revolution on the turret before unending out of correction and it moved maybe an inch. I then used Kentucky windage because I hate leaving the range with ammo and put the next 14 rounds into about a silver dollar. This tells me that my mounting is solid even with only three screws but I can't figure out why I ran out of correction.