Broz the farthest place I have to shoot right now 860 yards and I have never had to readjust a scope for vertical tracking using this method out to this distance. If you are missing left or right then I would be looking for some unnoticed wind currents or some kind of bad shooting habit (maybe even the mysterious spin drift).
Broz you are right about marking the scope, I forgot to mention that. I cut two pieces of electrical tape to a sharp point to create a couple of pointers and I stick one on the scope ring and one the scope tube. I guess a pencil mark would have been a lot easier but then again I am always trying to over complicate things.
MontanaRifleman I agree that the method that you described is a good way line everything up if the levels are accurate and nothing gets bumped, but the method that I described will prove that the scopes vertical travel is correct without a doubt. I also like to shoot a group around 7 moa and one around 15 moa to make sure everything tracking correctly. Like I mentioned before I can only shoot out to 860 yards right now and 20 moa will get me there, that's the reason I use 20 moa when checking my scopes. If you would like go to the limit of your scope's elevation you can see what effect it has on your tracking. Some scopes will do some crazy things once they get near the end of their travel.
Wouldn't it be possible to set up or identify a vertical line at the house or at the range, set your rifle in a vise with the anti-cant device level, aim at the top of the vertical and then run the elevation and see if it stays on the vertical?
I think I am going to set up a weight on a rope about 50 yards out the back door and give it a try. If the scope tracks right down the rope and the anti-cant is set level then there can be no question.
BTW, it can be awfully hard to tighten those anti-cants down with the bubble exactly right.
If you can read this, thank a teacher.......if you are reading this in English, thank a soldier.
Woods if you have way to keep the rifle in exactly in the same spot it will work. With a good vise you can do the same thing. If the rifle will return to the exact point of impact after cranking on the turrets few rounds then it will be steady enough to check the tracking.
I don't see, short of shooting your rifle, how you can be certain the scope isn't canted a small amount. If the scope mount holes aren't drilled and tapped precisely centered with the center of the bore when the mounts are level you have a problem. It could be small it could be large. Then, ideally, the center of the bore, the mount holes, and the center of the scope should be in line, and plumb when you're ready to shoot.
I've never been able to determine how to discern all that in my shop.
I don't take this subject lightly, but I don't have enough experience to know what's good enough, nor how badly it will affect you if you only level your scope reticle without insuring it's lined up with the centerline of the bore when the whole rig is plumb.
i'm gonna throw a monkey in the wrench here. i shoot a group at 100 yds, draw a perfectly verticle line, go up about 25 MOA. shoot another group. but i like to see the bullets hit about 1/2" to the left of verticle. this counteracts for the spin drift.
Now in most of the methods mentioned here, that I read anyway, it seems that everyone is assuming the scope reticle itself is mounted properly in the scope so they are in-line with the adjustments. Has anyone ever determined that their crosshairs were canted in relation to the adjustment movement??? I have a Mark 4 that seems to have this affliction. I spent a great deal of time leveling that bastard and from my 600 yard zero I can crank down to 100 yards and be shooting 4" to the left. I had a talk with a gentleman from Premier Reticles about this and he thought that was a common problem as the reticle in the Mark 4 is fitted in a keyway. Well the slot, or protrusion, on the reticle to fit that keyway has a little slop in it, and it was very common for the assembler to lock the reticle in the tube with it canted (the retainer twisted the reticle to one side of the keyway).
So now I was thinking of getting my rifle locked down in a padded vise where the scope/rifle was perpendicular and walking the elevation up a plumb line at a distance and correcting the 'cant' of the scope by trial and error...