Long range precision shooting is a complex art form. If you’re going to be successful you need to lay certain foundation stones in advance. Now one of those foundation blocks is making sure that your scope is true to the rifle.
Let's say that you’re used to doing this just by eye-ball and you get within a degree, which would be pretty good if you’re just eye-balling a scope level to your rifle. If you’re using a reticle based system, and you’re shooting 1,000 yards, let's say that your hold is 8.5 mils, at 1,000 yards, but if you had a one-degree error in the cant of your scope relative to the rifle, you would be as much as five or six feet laterally off the target. Out in space. So that is why it is so important to invest the time up front to perfect the truing of the scope to the rifle.
Secondly, the rifle has to be true to the earth and that is why we have this spirit level. I’ve got a brand new Horus Vision Raptor here with an H25 reticle and we’re going to true this thing up so it’s ready to mount on the rifle. Now I know what you are thinking. Why isn’t he doing this on the rifle?
Well you are going to get a better result doing it on a fixture. Now, not everybody has a scrapped upper receiver, which is what I’m using to hold the scope, but let’s go over this briefly.
I’ve got a grinder stand here, which is pretty heavy duty, and I’ve got a relatively inexpensive mill vice. So this gives me a very stable, solid platform to do this on.
You could get an inexpensive quad rail hand-guard and squeeze it in here now that it’s square from side to top. So this entire assembly becomes the fixture. Now before we adjust the scope you’ve got to true the fixture.
So let's put my level on top of the rail of this receiver. Check that, if it’s off I’m going to shim it. Looks good. What’s the next thing?
Well I need to find a point in space out here that I know is true. Either perfectly level horizontally or for example, a plum line that is perfectly vertical. In this case I’m down range there, I know that the top of one of those target stands, actually a plate rack down there is perfectly plum because I checked it. So that is what I am going to use as my registration point to accomplish the truing of the scope to the rifle.
So I’ve got this scope mount here. I’ve got actually one of our new extended mounts. And I’ve just attached the rings and they’re just snugged up a little bit, and that allows me to tap it, and perfect it.
So I’m going to look through here, actually using my screw diver as a mallet, and I’m going to perfect the level of the scope right to that registration point.
Once I’ve got it now I’m going to just start snugging down one of these straps, and while I’m doing that I’m going to keep checking that I’m still true, because sometimes when you move the strap it will move the scope.
So it’s true and I’ve got it locked in, now I’m good. Now I can tighten the whole thing.
Now that I know the scope is true to the world, I want to make sure that this level, this spirit, is level. Now that is the second part of this equation. I need to get that true. So I’m going to adjust the level, until that bubble shows perfectly level to the scope, and I’m going to tighten that up.
So now I know the scope will be true to the gun and once I have the scope true to the gun, now the spirit level is going to allow me to true the rifle to the earth, because the vector of gravity is what the principal is on all your ballistic software. It assumes that your rifle is perpendicular to the gravity vector.