Glad you got me to do that because two of my scopes have a cant on them and I got to fix them.
You can see on the t-bolt that there is no flat on the action to set a spiritual level on… so, I use the lazy/expedient design of modern factory stocks (lack of toe and cast) to drop a plumb between centres of the butt screws. Not ideal but better than guessing the level. I guess you could put it in a vice and call it good enough but that’s how I got the cant on that scope.
If you have a flat below the scope turret and a flat on the top of the action (or a rail), you can also use a steel rule to set the scope level as below. Obviously, this rifle doesn’t suit that method but there’s a pic for illustration purposes anyway.
Dammit… Late night posting after too many beers… though you were talking about mounting the scope…
I honestly don’t think I’d have time to check a scope bubble while hunting. Handy for longer range, I guess. Lots of people use them for f-class, etc but I prefer tuning my ‘internal level’ and training my eye to see cant.
I put a level and or a bubble level on the pic rail. I set up a brick on a rope hanging from a tree 500 yrds away and true the scope reticle to the 500 yrd plumb line when the rifle is level. I then fit a bubble level to the scope and make sure it shows level at this setting.
So I take it that plumb line is only useful when the butt has two screws holding the recoil/butt pad and the screws are aligned. Sort of old-school stocks if you will. Won’t work on most modern stuff? For example, one I have where recoil pad slides in to the chassis, rather than screws in.
I saw a video on YouTube that took this approach. Plumb line along the wall near the eye relief and torch shining through the objective lens projecting the reticle onto a wall. Then just fiddle with scope to align windage line to the plumb line.
You could just measure two center points on the butt plate. As I said, it’s just a work around I came up with to use when there is no flat surface on the horizonal plane to set a level to.
The advantage of doing at a long distance is it gives more precision. You scope reticle lines are much thinner in comparison to the object. Also just like MOA if you are out that little bit it is amplified at distance so you can get a finer adjustment.
Surprisingly I found and learnt that not all bubble levels are created equally. This was after buying a half dozen from China I got them off different suppliers and even in the cheap end there are differences. The Tube the bubble in is where it is all at. Are the surfaces straight? otherwise bubbles get stuck. The surfaces of the tube can have stiction which makes the bubble slow to respond. I am sure there is a heap more. I did find that there were amounst the good ones for builders some specs. Non for Rifle use. I have observed the issues on my guns. On my comp gun I have two and I am now used to how they behave and just where they sit when I am vertical.
At long range cant is a very important factor. If there is a mathematician in the house work this example. At 500 yrds the normal vertical adjustment from 100yrds is 8 MOA if you are 3 degrees off vertical what angle have you now added to your windage? By 1000 yrds the vertical compensation is now 29 MOA what have you done to your windage with the same 3 degree error?
Vertical is vertical. Doesn’t matter whether your plumb line is immediately in front of the scope or tang sight staff, or 500mtr away. Unless you enjoy the walk, save yourself the time.
Yes, cant, or lack of it, is very important at almost all range distances. Think rainbow trajectories for heavy, or slow projectiles. 40gn rimfire @ 300mtr, or 500gn 45-70 @ 1,000mtr.
I disagree @oldAG when you wind your scope up to maximum magnification like it would be when taking a long distance shot, things like parallax, eye relief all become more sensitive it is at these settings and distances that it is best to set up your scope cant.
So how do you guys ensure your rifle/action is true on the x/y axis before plumbing or leveling your scope? After all, it is pointless setting a level on a scope that is mounted to a rifle that is canted.
You are free to disagree, but, parallax will NOT change the cross-hair alignment, eye relief will NOT change the alignment, magnification will NOT change the alignment.
All that is required is that you can superimpose the cross-hair on your plumb line, at any distance.
