It’s probably cant. Do a tall target test like recommended above.
Levels are just a baseline. Setting the rifle up for consistent hold, then using a plum bob to plum the reticle is best after initial set up.
ps, don’t worry about rifle cant, just concentrate on a hold that you can repeat every time you get behind the rifle. After plumming the reticle, set your anti cant level on the scope tube.
All confirmed with a tall target test of course.
Jim, same thing. Another note, I prefer my tall target test to be slightly left so I don’t have to mess with spin drift. Takes another thing out of the equation since mine are for hunting and not br score
I owned an expensive Luepold scope. I wasted a lot of ammunition trying to figure out a similar problem. I ultimately discovered that the reticle was NOT squared with the scope body. When making either elevation or windage adjustments they were both way off. I replaced the scope.
The last several rifles that I have set up had the scope reticle/scope level adjusted by projecting the reticle on my basement wall with a plum-line, and aligning the reticle and level to the plumb-line. ALL the 100 yard tall tests performed on each in the field were “nuts on” with no further adjustment required.
You might check the alignment of the scope base mounting holes vs the barrel. Often these are not in perfect alignment and you have the condition you describe. In this case the Burris Signature rings with the inserts are your friend. I have used a 30" Al rod 1" in dia to test the alignment of the scope bases before. I have also made sure the scope reticle was centered and them use a bore sighter to see it they align.
Like other said that would be a ton of cant.
I have found out that even if I think it’s perfect at 100 it’s off a bit at 200. So I e since started using my side to side zero at 200 with a calm day. Then when I go back to 100 it’s always on. 300 yards seems like you may be off a smudge left to right with the wind not helping.
Try a segway leveler. It’s only about $20 and works great. I have no issues with that setup at 300 yards.