Rifle Scopes Scope Problem

[BMoe]

Had a Weaver Grand Slam 3x10 that was recommended here in the past on a 22-250 for coyote hunting. Well I got an AR with a 20MOA base (Nikon) and installed this scope. It took all of the down adjustment and was still shooting 8 inches high at 100yrds. Then I went out and bought a 0 MOA Nikon mount and with the scope at the lowest setting is still shooting 2.5" high at 100. Any suggestions?? The scope is holding zero and always has. I just don't understand why it isn't going up in elevation when using the 0 MOA.

 

[BMoe]

Re: Scope Problem

Would putting a shim in the front scope ring bring up the elevation?

 

[stranded]

Re: Scope Problem

I'm not an expert, How tall are your rings? If I understand you putting a shim in the front ring sounds bad as it could stress the scope. Too tall of rings might place scope to far from the bore to allow propper sighting in. Pics. would be heplful.

 

[Frank]

Re: Scope Problem

If its a one piece base, then shimming the base will not put any stress on the scope. A set of two piece bases would theoretically place stress on the scope tube. Strange that you are only getting about 5.5 MOA change in elevation when going from a 20 MOA mount to a 0 MOA mount. Keep us posted on what you find.

 

[nimrod12]

Re: Scope Problem

easy fix is to use burris signature rings. they come with polymer inserts that can give you adjustments up to 10 or 20 MOA(can't remember which). check them out....easy fix.
Nimrod

 

[Graham]

Re: Scope Problem

None of this makes any sense: Not the scope adjustment; not the shims; not the inserts.

When I get a scope that is broken I send it back.

Meanwhile, shims and inserts are usually the topic of a more robsut discussion by self-styled experts on AR15.com.

 

[Exo]

Re: Scope Problem

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Graham</div><div class="ubbcode-body">
Meanwhile, shims and inserts are usually the topic of a more robsut discussion by self-styled experts on AR15.com.

</div></div>

^^ made me laugh...


if its possible, have you tried putting the scope on another rifle to verify you are having the same issues? what kind of AR is it...

 

[BigOhio]

Re: Scope Problem

Sounds like either the AR already has some angle built into the rail or the rail is not quite right.

 

[sib1948]

Re: Scope Problem

When changing rifles, did you start by adjusting the elevation knob to the midpoint of it's elevation range before putting it on your AR? Just might do the trick.

 

[samnev]

Re: Scope Problem

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: BMoe</div><div class="ubbcode-body">Would putting a shim in the front scope ring bring up the elevation? </div></div>

IIRC putting a shim under the front ring will cause your scope to look higher on the target so to hit point of aim you desire you bring the rifle down which effectively lowering your scopes elevation which should help cure your problem. I have used a piece of tin from a coffee can when I had the same problem with a new scope. I don't remember exactly but it brought my elevation down about 15" IIRC. Good luck with your problem.

 

[jtv3062]

Re: Scope Problem

Start with this video.

[youtube] <iframe width="560" height="315" src="http://www.youtube.com/embed/aoW5bHQqgis" frameborder="0" allowfullscreen></iframe> [/youtube]

 

[BMoe]

Re: Scope Problem

Thanks for the suggestions. AR is a Stag M3. The scope was on a Tikka T3 lite with 0 MOA mount. No problems at all. Moved scope to the AR with 20MOA nikon mount and the scope was bottomed out and still shooting 8" high. Changed to a 0 MOA mount and still bottomed out and shooting 2.5" high.

I'm gonna try taking the scope off and setting it near zero. If that doesn't work I may try a peice of tin,etc and shim the base.

Thanks Again

 

[scudzuki]

Re: Scope Problem

Shimming one end of a picatinny mount will rotate the mount as it raises it.

It's really not a good thing to do.

Joe

 

[Ffej]

Re: Scope Problem

Don't mean any offence by this, but are you sure the mount is facing the right way? It wouldn't explain why you're still shooting high with your flat mounts, though.

Since you're using two Nikon mounts for your tests, are they making the proper contact with the Picatinny rail? Do you have another non-Nikon mount you can test with as well?

 

[BMoe]

Re: Scope Problem

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Ffej</div><div class="ubbcode-body">Don't mean any offence by this, but are you sure the mount is facing the right way? It wouldn't explain why you're still shooting high with your flat mounts, though.

Since you're using two Nikon mounts for your tests, are they making the proper contact with the Picatinny rail? Do you have another non-Nikon mount you can test with as well? </div></div>

Its mounted the right way and no offence taken. I'll watch the vid in its entirity. Don't have any other mounts available at this time.

 

[jtv3062]

Re: Scope Problem

Never mind about my posts. I thought you had a bolt action.

 

[BobD]

Re: Scope Problem

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: BMoe</div><div class="ubbcode-body">Thanks for the suggestions. AR is a Stag M3. The scope was on a Tikka T3 lite with 0 MOA mount. No problems at all. Moved scope to the AR with 20MOA nikon mount and the scope was bottomed out and still shooting 8" high. Changed to a 0 MOA mount and still bottomed out and shooting 2.5" high.

I'm gonna try taking the scope off and setting it near zero. If that doesn't work I may try a peice of tin,etc and shim the base.

Thanks Again </div></div>

**************
I would assume The problem is that your scope does not have enough internal adjustment to use an inclined base. With your windage optically centered, your weaver will only have 20-24moa elevation adjustment from center (total being 40-44). 20 moa of downward (bullet impact) of that travel lost when installing the incline and trying to achieve the same zero. Once you've used windage to zero your rifle you've effectively lowered that figure again.

Essentially, by adding the mount you have placed the top of the scopes sight picture where it would naturally be centered (bottomed out literally by half). The problem is that you have no more adjustment to move the reticle higher (bullet impact lower) to still maintain a 100 yard zero. You should now however have probably close to or just shy of 40 moa (impact up).

When using an incline base with a scope that has minimal internal adjustment it can be difficult to achieve a closer zero. It's optimal to have more adjustment when using an incline as even if you we're able to achieve zero at your bottom you would be looking through the bottom most section of your scope which would degrade your sight picture and restrict windage movement. It can be achieved with less than optimal adjustment 60moa, but you should have 80moa+ if you want the flexibility of longer distance with a closer zero.

That's why you were able to zero on your Tikka without issue. Because your shooting an AR
I would suggest considering a 50/200 yard zero if you intend to keep the current setup. It's nice they cross paths at these distances and might be worth giving thought to.

Or consider going to a mount without incline if you don't plan on longer distances and prefer the 100 yard zero.

Hope this helps,
Good luck-

 

[BobD]

Re: Scope Problem

I somehow skipped over that you tried using a traditional mount. If that was on the AR, you should have been able to zero just fine.

A quick fairly easy test to check which is your problem:

In either mount, set your rifle up in a rest at 25 to (preferably) 50 yards. Place a few indexed targets atop one another. Since your scope is already bottomed out (reticle at its highest point) bring elevation up to its max. Start with your crosshairs at the top of the highest target and measure how far down the reticle will travel. If your windage is centered, you should still have the full adjustment range to move impact up 41 or 48 moa I believe. Translate the distance your reticle traveled by either converting or simply measuring with reticle (if its ranging).

That should hopefully rule out if something has been seized up in your scope. It doesn't make sense that the difference between your standard mount and incline is less than 6" at 100 yards unless there is some appreciable difference in height between the two you are using. The standard mount would have to be much lower than the M223 to make up for almost 14moa of unaccounted incline.

I would double check to make sure you windage is centered so you have all of your adjustment available. Hate to suggest it, but even bottoming out with a 20 moa incline (and little adjustment), I wouldn't think you would be that high.

I must retract part from my last post, you would sure have the same issues but I don't believe to this degree. It may still be a contributing factor but its likely something else has happened here.

 

[BMoe]

Re: Scope Problem

Thanks for the suggestion Bob. If weather permiting, I'll try that as well. I just hope the scope isn't jacked up. The last sight in was dead on at 25 yrds on a solid rest. may have to try the 50 yarder and zero for 200. I just want to get back out with the rifle and zap some more coyotes.

 

[BMoe]

Re: Scope Problem

Got up this am and got out before the snow hit. Tried remounting the scope and didn't help. Played with elevation knob and same result. Made a plastic shim and placed it in the front scope ring. It worked. I know its not at all the best solution, but at least I can get back out with it and shoot some coyotes till I can really get it figured out. Got re-zeroed at 100 yrds just as the snow started to kick in.

I'll have to re-evaluate the situation when more time allows, but like I said, I can go put some coyotes down.

 

[RickR]

Re: Scope Problem

Hello,
"Shimming one end of a picatinny mount will rotate the mount as it raises it."

Can you explain this? I can't visualize how this would happen. Thanks.

Regards,
Rick

 

[scudzuki]

Re: Scope Problem

A mount on a Picatinny rail is located vertically by the flat top of the rail, and horizontally by the angled fixed side of the mount, that is, the angled facets that face down. The 45 degree angled edges of the Picatinny base directly adjacent to the flat top are really just clearance; a Picatinny mount functions essentially as a dovetail interface.

Raising the mount pushes it sideways because the angle on the side of the rail wedges it away from the center of the rail.

Raising one end of a long mount will push the mount sideways at the shimmed end, and if the other end is not shimmed, it is in its original position sideways, so the mount is rotated relative to the rail.

Joe

 

[ken226]

Re: Scope Problem

If its the Nikon ar223 20 moa base, i owned one for about 20 minutes. I mounted a scope in it and could easily see with the naked eye that the scope was pointed to the left. I took the scope back out and tossed it in the garbage.

I bought a no-name mount on ebay for 50.00 to replace the Nikon. It was dead nutz accurate, strait and centered. With the scope mechanically centered in its adjustment range, the first round was 1 1/2 inch high at 100 yds on the Wangdong (just a guess) brand mount.

 

[rcmigpilot]

Re: Scope Problem

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: ken226</div><div class="ubbcode-body">If its the Nikon ar223 20 moa base, i owned one for about 20 minutes. I mounted a scope in it and could easily see with the naked eye that the scope was pointed to the left. I took the scope back out and tossed it in the garbage.

I bought a no-name mount on ebay for 50.00 to replace the Nikon. It was dead nutz accurate, strait and centered. With the scope mechanically centered in its adjustment range, the first round was 1 1/2 inch high at 100 yds on the Wangdong (just a guess) brand mount. </div></div>

I had the same issue with the 20 MOA Nikon mount that you did, but my solution was not quite as drastic. The Nikon mount has three major parts, the ring caps, the mount itself and a lower section that the bolts run through that clamps the mount and to the scope rail. The base will go on turned either way, but will only align the scope properly when its in one direction. I spun the base around and had no issues zeroing the scope. I actually really like the mount, it puts the scope at the perfect height for me.

 

[jerry1]

Re: Scope Problem

Bob has it right.