Rifle Scopes Optical center not in the middle of the (elevation) adjustment range?

[BurnOut]

I have a scope (not going to name the manufacturer at this time; don't want to start a needless bashing thread) that is exhibiting some odd behavior. Specifically, when it is zero'd on my rifle (POA = POI) at 100 yards, I find that I am using ~75% of the total elevation travel. That is to say that the specs for the optic (and my own knob twirling) show over 20 MILs of total elevation travel, but when it is zero'd, I'm using about 15 MILs... which means that I have just a little over 5 MILs of elevation travel for when I want to stretch things out.

Now, I know that it's not uncommon to have scopes where the zero is off of dead-center in the elevation travel range by a little bit, but being off of center by ~5 MILs seems excessive, no? I have engaged the manufacturer who has had me verify the total elevation travel (within spec), remove the zero stop (thus eliminating it as a variable), re-check that my rings (ARC M10s) are properly seated in my (Warne 0 MOA) pic rail, and bore-sight the rifle. I've done all that, and am still experiencing the same issue. I am continuing to work with the support team (I want to give them a chance to get this worked out before I start naming names), but is there anything else that I'm missing? I have verified that the pic rail is correctly installed and making good contact with the (Howa mini) action as well.

Any thoughts/suggestions are welcome.

 

[Hollywood 6mm]

Have you tried it on another rifle entirely, or tried another scope on your rifle? Even if the rail is installed correctly, there could be some other machining issue you can't see that is causing the misalignment. Said issue could be in the barrel to action alignment, action to rail, or even the bore inside the barrel. Edit: It could also be an issue with the Warn rail itself.

I had a similar problem years ago with a Weaver rail, and was able to correct it by bedding the rear of the rail. When I hand tightened the two front mounting screws of that rail, but left the rear screws out, the rear of the rail was lifted a significant distance away from the action. Bedding it to remove that gap fixed the issue, but it wasn't long before I tossed it and got a better quality rail to replace it.

 

[EXTREMEPREJUDICE]

but is there anything else that I'm missing?

You need a canted base, very common by the way. To gain back your 15 mils you need approx. 50 MOA so a 45 MOA base is probably your best bet.

 

[Hollywood 6mm]

You need a canted base, very common by the way. To gain back your 15 mils you need approx. 50 MOA so a 45 MOA base is probably your best bet.

A 0MOA base shouldn't be causing him to be 5MIL off of the center of the adjustment range. While a canted rail would help, it would only be masking the problem, unless the current rail itself is the actual issue. If the current rail is the actual problem, then going too far on the cant would put him at the opposite end of the adjustment range, where he may end up with clarity issues and distortion, depending on the optic.

 

[BurnOut]

Have you tried it on another rifle entirely, or tried another scope on your rifle? Even if the rail is installed correctly, there could be some other machining issue you can't see that is causing the misalignment. Said issue could be in the barrel to action alignment, action to rail, or even the bore inside the barrel. Edit: It could also be an issue with the Warn rail itself.

I had a similar problem years ago with a Weaver rail, and was able to correct it by bedding the rear of the rail. When I hand tightened the two front mounting screws of that rail, but left the rear screws out, the rear of the rail was lifted a significant distance away from the action. Bedding it to remove that gap fixed the issue, but it wasn't long before I tossed it and got a better quality rail to replace it.

Hmm... that's an idea. I do have other optics I can throw on there as a test. I'll also check for the condition that you mentioned with the Weaver rail. I don't recall anything like that when I was installing the rail, but then I don't specifically recall looking for anything like that, either.

 

[BurnOut]

A 0MOA base shouldn't be causing him to be 5MIL off of the center of the adjustment range. While a canted rail would help, it would only be masking the problem, unless the current rail itself is the actual issue. If the current rail is the actual problem, then going too far on the cant would put him at the opposite end of the adjustment range, where he may end up with clarity issues and distortion, depending on the optic.

That's kinda my thought is that I could go to a 20 MOA rail (the only other option that I am aware of for this action), but that seems like more of a bandaid than properly addressing the issue.

 

[withoutwarning]

I got the same issue with my Q The Fix and Leupold Mark 6 3-18.
I’ve got 8 mils left of elevation on a scope that’s supposed to have 15+ mils of travel from the optical center. The turret will dial 12.5 mils but the reticle stops moving at 8 mils.
Regardless I hate this scope and I’ll be sending it back to get fixed and then selling it after shot show and these new grid reticle scopes from nightforce and SB come out.

 

[ShtrRdy]

It's possible that the barrel is not installed square to the receiver.

Using another known good scope on this rifle/base/rings should tell you which direction to look next.

 

[koshkin]

While it is possible that the scope is screwed up, almost every time I have run into a situation like this in the past twenty years, it was a problem with the action not being square or the barrel.

Try this scope on another rifle or another scope on this rifle.

ILya

 

[BurnOut]

I'm going to try another scope, but at this point I'm thinking that the barrel/action interface is probably not the issue; I recently had it rebarreled at a reputable shop. I'm not quite sure what to think at this point, but I'll certainly post with my findings once I try another scope.

 

[withoutwarning]

I'm going to try another scope, but at this point I'm thinking that the barrel/action interface is probably not the issue; I recently had it rebarreled at a reputable shop. I'm not quite sure what to think at this point, but I'll certainly post with my findings once I try another scope.

Mine shit it self today.
Just wasn’t holding zero. I’m at the limit of the horizontal travel of the scope and my shots are now 1.5mils left at 100m. Can’t turn it anymore to zero the scope. The dial is only on .5mils left so it’s not the dial. The dial has 5mils left and right.
I’d be sending it back and just getting them to replace it.

 

[Hairy Biker]

Don't blame the scope if the mounting system is wrong, or if the barrel to action fit is off centre.

Get your checklist out and check and re-check before blaming the scope. 30 mins of concentrating is worth it and you might find it is time for a new rifle.

If you do end up with a new and better made rifle - blame Snipershide.

 

[Subwrx300]

My guess is barrel/base aren't square on the same axis. It only takes an incredibly small amount of deviation off square to produce a damn large change at muzzle. While the exterior of barrel may be square, if the bore is pointed slightly up/down (ie not perfectly centered) it produces the same effect.
Try another scope and see if a same issue occurs.

Also, you cannot rule out rings until you swap to other rings. One could be taller/shorter slightly causing part of the issue. Only way to on be sure is test another optic and mount:. Same problem, it's the rifle, if not, somewh between scope, rings and interface with rifle.

Had a buddy say his scope/gun was screwed up with no windage left in scope. Took one look and noticed he had one ring bolt on right side and one on left said (facing 180 degrees from each other). Flipped the ring back so both matched and rifle was dead center in tracking.

 

[krw]

What is max anyone has seen where bullet is not leaving the bore “straight line” because of bore offset. Last 2 bbls I have had screwed on, I bought precision range rods and we attempted to “time” bore to “High” at 12 O’Clock. It didnt work out exactly as planned tho

 

[Subwrx300]

What is max anyone has seen where bullet is not leaving the bore “straight line” because of bore offset. Last 2 bbls I have had screwed on, I bought precision range rods and we attempted to “time” bore to “High” at 12 O’Clock. It didnt work out exactly as planned tho

I've had an AR barrel be 12MOA left and 10 moa high (extra travel useable) from "mechanical center" of scope. No way to tell if rings, upper or barrel caused this but presumably most barrel as the prior barrel was only off 2-3 MOA from center.

Here are calculations for a 22" barrel with .1" offset from perfect square/true. My geometry is a bit Rusty but should be close (if someone knows Geometry well and sees an error in assigning angles/values, feel free to correct).

But the effect is a 15.6 MOA/5MIL shift from perfectly centered.

 

[BurnOut]

Just tried another scope (from the same manufacturer, no less... just a different model that happens to share the same elevation range spec), and it looks like my original scope has an issue. The only change I made was to install the "spare" scope, and it bore-sighted pretty damn well out of the box with the dials set to 0/0. I was able to confirm ±10 MILs of elevation adjustment from the bore-sighted zero.

The saga continues.

 

[BCP]

Leupold? I had one like that the reticule was in the way upper left of the lens so it took a shitload of right turns to get it on paper. Send it back and they'll fix it.

 

[Hollywood 6mm]

Just tried another scope (from the same manufacturer, no less... just a different model that happens to share the same elevation range spec), and it looks like my original scope has an issue. The only change I made was to install the "spare" scope, and it bore-sighted pretty damn well out of the box with the dials set to 0/0. I was able to confirm ±10 MILs of elevation adjustment from the bore-sighted zero.

The saga continues.

Any company can let one slip through from time to time. The difference is in how it's handled. Assuming it's a known, reputable company, it'll be made right.

 

[BurnOut]

Any company can let one slip through from time to time. The difference is in how it's handled. Assuming it's a known, reputable company, it'll be made right.

Exactly my thought, which is why I'm working with them rather than throwing them under the bus and raising hell on the Interwebz. As a rule, I think that too many folks online will raise a stink without giving the manufacturer and/or vendor a chance to make things right.

Really, the only reason I started this thread was in case there was something simple/stupid that I was overlooking.

 

[koshkin]

Exactly my thought, which is why I'm working with them rather than throwing them under the bus and raising hell on the Interwebz. As a rule, I think that too many folks online will raise a stink without giving the manufacturer and/or vendor a chance to make things right.

Really, the only reason I started this thread was in case there was something simple/stupid that I was overlooking.

That's the right way of doing it.

ILya

 

[Hollywood 6mm]

Exactly my thought, which is why I'm working with them rather than throwing them under the bus and raising hell on the Interwebz. As a rule, I think that too many folks online will raise a stink without giving the manufacturer and/or vendor a chance to make things right.

Really, the only reason I started this thread was in case there was something simple/stupid that I was overlooking.

I wish more people would do that.