If this is in the wrong section, apologies - perhaps one of the mods could move it?
I went to a range to today and have been struggling to understand the results I've seen with the rounds I was testing.
I was testing three different reloads for safety and to find powder maxima for them, but through the course of the day, I saw evidence of canting errors in my shooting. The fastest of the reloads shot high and to the right. The middle one for which my rifle is currently zeroed shot correctly in the middle and the slower, heavy load shot down and to the left. My horizontal point of aim was always the same (i.e. the vertical line running through the bullseye), however.
I didn't twig about this until I got home, but that diagonal line across the target is most likely caused by canting the rifle clockwise (from the shooter's perspective) and, sure enough, when I just took the gun out of the cabinet to look at it, the scope is misaligned slightly in the counter-clockwise direction (again, shooter's perspective). This means that I was turning the gun off-vertical to get the scope vertical line to appear, well, vertical.
The net result is that I need to reset the position of my scope so that the vertical scope line runs perpendicular to the rifle's bore.
I'll do this, but I'm aware that it could have been mis-set for some time and that I probably created the error in the first place by not mounting the scope in the proper alignment. I doubt the scope has slipped in the mounts - they've held fairly well if my usual load and it's basically static zero is to be believed.
Therefore I'm after suggestions: when I'm resetting the scope, how can I best ensure that the rifle is correctly aligned, vertically, and then match the vertical axis of the scope to it, so that I don't end up simply setting a different misalignment and canting the rifle in some other way? Any techniques / tips will be very welcome.
I'm aware I'll need to re-zero each of my loads when this is done. Are there any other consequences of resetting my scope that I haven't thought of?