Originally Posted by
Mauser308
Those the Leupold windage adjustable bases? If so, yuuuck.
Another possible culprit is the rear base not being properly centered, and the scope adjustment is hard over to one side to compensate and get the POI corrected so that the internal tension springs on the reticle adjustment aren't applying the correct tension. The recoil of each shot bounces the reticle from limit to limit giving double grouping...
The rotating front ring in the Leupold windage-adjusting design means that the front ring can move in the base as well. It might not wiggle apparently when you check it, but it doesn't take much movement to give you a different POI at 100m. That setup would be a a prime, possible culprit to me - I've found issues with about 3 or those setups now (usually dodgy installation). The front base, front screw (where the hole through the action is above the barrel tenon or barrel threads) needs to be carefully shortened down so that it doesn't bottom out on the threads on the barrel before the head of the screw bares down on the front base.
I would disassemble an inspect the scope bases and mounting system (again) and check the lateral position of the rear base (it must be as near to centered as possible) and then check the front base. Remove the rear screw from the front base and then see if the front base is still tight against the receiver. If not, you might have just found the problem. If it is, try a one-piece base and weaver rail type rings.
From there, you need to try another scope - the current one might be toast. I've seen the windage error twice now with the rear base, both times the scope (Leupold) had to go back to the factory because the adjustment system had been damaged. The 3rd time, the front base front screw hadn't been shortened and the front base wasn't fully secured down...