Rifle Scopes How important is it to be close to mechanical zero?

[vincent7]

So I checked a few rifles where I had the rifle zeroed at 100 for windage and elevation. I set the dial to zero after POA was POI, and then looked how much windage range I had on the dial in either direction.

As it turned out, have a few rifles where there's about an equal adjustment range left and right, but there's also a few where i have for instance a half turn to the left to work with, and a turn and a half to the right.

What's considered out of spec / too much of a difference between the left and right adjustment after zeroing the rifle, and what potential negative effect is there when you have for instance half a turn in 1 direction left, but a turn and a half in the other direction?

 

[CoryT]

The main issue with being out of center is getting windage when you dial elevation near the limits of travel. Since the erector is a tube inside the main tube, if you are not centered as the elevation is dialed on you can have the cell push on the outer tube. I just did a tracking test for a friend where the scope delivered .2 mil of windage for every .1 of elevation after hitting 10 mils up.

How much is too much? That will depend on the mfg and the diameter of the cell and outer tube, combined with the total travel in each axis and how much travel you have after zero, compared to how much you need for the cartridge. In a hunting application it's probably never a problem, even if you nearly pin windage in one direction. If you get zeroed, you won't be dialing anything so it's all good. In an ELR setup is you are not perfectly centered you may well have an issue as you near the end of travel.

 

[jp_over]

+1 on above. As a hunter, outdoorsman I never worried about it but now that I have the knowledge it's a quick and painless process to check before sighting in.

 

[toader]

I try to stay as close as I can, but I don't worry if I'm off slightly.

 

[vincent7]

Got it, thanks for the input. Thinking I might try some Burris signature zee rings to address one rifle where it's the worst.

30mm tube; Riton Mod 7, MOA scope. SFP

3.7 turns one way and .6 turn the other.

 

[Denys]

Let me add some further thoughts on this subject; I have some opinions.

I haven't a clue what is "in spec" for this and that will most certainly depend on the manufacturer and they will blame other things for the scope not being near the center. As they should. Unless a riflescope is grossly defective, the mechanical zero of the erector assembly will be where it is equidistant from the outer tube. Now, when you mount a riflescope on a rifle, you hope that the receiver on which you mount the scope is in line with the bore of the barrel, both in elevation and in windage. You also hope that the rail is parallel, if there is a rail, and you hope that your rings or mount are all parallel and correct. You can see where I'm going with this; it's not so much the scope as the way it's mounted on the rifle.

If any of those things are off kilter, the chances of the scope being centered mechanically and optically on target slowly (or rapidly) go out the window. We hear stories of receiver drilled and tapped and visibly off line. It doesn't take much to make the whole thing catawampus. Please excuse the technical term.

At any rate, it is always my goal to mount a scope on a rifle in such a manner as to have the scope as close to mechanical zero at the distance at which I will mostly shoot the rifle. The reason for wanting that is that, optically speaking, you will get the best IQ out of your scope when it is a mechanical zero. That's where the very best IQ is present. The other comments about adjustment range and spring compression and so on, are all very valid but IQ is the most important reason for me.

For example, my F-TR rifle has the riflescope very near mechanical 0 with a zero at 1000 yards, because that's where I shoot it the most. To achieve that, I used a combination of a 20 MOA rail and Burris XTR rings with the proper inserts.

The Burrris Signature rings are a great way to help you achieve this, especially of there is a windage displacement as well as an elevation issue.

 

[308pirate]

So I checked a few rifles where I had the rifle zeroed at 100 for windage and elevation. I set the dial to zero after POA was POI, and then looked how much windage range I had on the dial in either direction.

As it turned out, have a few rifles where there's about an equal adjustment range left and right, but there's also a few where i have for instance a half turn to the left to work with, and a turn and a half to the right.

What's considered out of spec / too much of a difference between the left and right adjustment after zeroing the rifle, and what potential negative effect is there when you have for instance half a turn in 1 direction left, but a turn and a half in the other direction?

Quit worrying about trivial shit and go shoot.

 

[vincent7]

Thanks again for the input. Just bought a set of Burris signature rings from the PX, will try them out. Curious about these rings and how good they work.

 

[jp_over]

Thanks again for the input. Just bought a set of Burris signature rings from the PX, will try them out. Curious about these rings and how good they work.

I've been using these for years on my air rifles and they're top notch. From the guys who use them on firearms I haven't heard any complaints. Overall great rings that allow lots of fine tuning to your point of impact without cranking the windage and elevation.

 

[Steel+Killer]

Go shoot the damn rifle and quit worrying about silly shit!