I bought a 12 VLP 223 with the fast 1-7" twist a year and a half ago or so. I started breaking the barrel in before mounting optics on it and picked up a Shaw 1-14" barrel in the same caliber to use as a prairie dog barrel (bought the gun with a 7" twist to use for distant target shooting). Mounted up a Viper 6.5-20x44 and attempted to zero the factory barrel. I bottomed out the adjustments in the scope trying to find paper at 25 yards. Still hitting a foot low at this range. Was planning on heading to wyoming to shoot some dogs, so I pulled the factory barrel off and put the Shaw on. Zeroed without any headaches and I shot it for some time. Last week, I got around to getting the factory barrel back on and the same issue remains. Shots are striking extremely low. The only thing I have found out of the ordinary was that both the recoil lug and barrel nut were gouged when taken off initially as if something was jammed between them when tightened down at the factory. I replaced the barrel nut (had a spare lying around) but left the factory lug in place when shooting the Shaw barrel. I only mention this because I found it odd, but it is not near severe enough to cause the issue I am seeing. My only theory is that the threads on the factory barrel are not perpendicular to the axis of the bore causing it to be out of square with the action? Any thoughts?

Nathan