scope problems - not enough adjustment

[cshooter]

Hi guys, I have 5x15 Bushnell Legend scope that has never let me down on my old 243. Then I bought another rifle with higher mounts( an AR15 upper in 25 wssm) and now i've ran out of adjustment. It shot center and 15" low at 100 yrds when I first put it on and I don't have enough adjustment to get it up to zero. I checked it out, then switched mounts. Same problem. Do you think it's the scope ? I have another old Simmons 44 mag 6x20x44 I could use on my 270 to see I guess, but I hate to. It's always been a good scope in the past, but I don't know alot about scopes either. I think the ar mounts are around 1 1/2", but that should'nt make that much difference should it ?

[Rick in Oregon]

It's most likely the mounts (or possibily rings) and not your scope, as the scope was fine on your 243. As a scope on an AR is so far away from the axis of the bore, the slightest miniscule amount of misalignment of the mount or mounting holes is greatly manifested by this distance, and a scope of known quality could be greatly affected and never be able to have enough adjustment to compensate for the mount alignment error. The lower the scope is over the bore of any rifle, the less any possible misalignment has an effect, and the less likely you are to cant the rifle.

Optically center your scope reticle adjustments prior to changing or removing anything (turn all the way to stop, count the clicks to the other stop, then use half the clicks on E & W, stop there, and it will be centered).

Fix? Either by shimming ( ) or replacing the mount with a well-known tactical brand known for it's quality and reliability, but it appears the mount you have now is the culprit.

By the way, how does a 25 WSSM feed through an AR?

[futuretrades]

I don't own an AR, but I had the same problem on both my Howa and Vangard. I had to shim under the rear mount to get the POI close to center so I could make the final adjustments. On the Howa, I had to use a .020 and a .002 shim under the rear mount. On my Vangard I had to use a 0.10 and two .002 shims under the rear mount. By doing this, I now have more than enough elevation adjustment on both rifles. As I stated above, I do not own an AR, but this is what I had to do.

Another suggestion would to be to put a shim of known thickness under the the scope on the rear mount, (between scope and ring). Just snug the scope in the mounts, and check to see if you are able to bring the POI closer to where it needs to be.

Whatever you do, I wish you the best of luck in correcting the problem.

[Clover_Shooter]

Or you could use a set of Burris Signature Rings with the Pos-Align Offset Inserts. on sale here http://www.midwayusa.com/viewproduct/?p ... ber=712472. This is one of the best systems for mounting a scope in a pair of rings. I used them to optically center for both elevation and windage at 400 yards on my XR100.

[cshooter]

Well, I had this same mount and rings on another ar15 upper and had no problem with the same scope in this way. I wonder if the upper is a little off ? It can't be off much because at 100 yrd it's about 2-3" low when I run out of upward adjustment. Or maybe the mounts got bent or something (should'nt have). I got pretty good groups too, with factory ammo. Will handload for it later when I get this all ironed out. Anyway, I don't quite understand what kind of shim i should use. I tried to slip a piece of plastic .02 thickness under in the rear mount between the scope and mount and could'nt get the top screws to align. I don't see how I could shim under the rear mounting screw and get it to fit the picatinny base on the rifle top. I don't think they make Burris signature rings for Ar15 mounting , or I did'nt seem to find any at Midway USA that would work. Maybe I need to take more time to study the Burris mount bases for a picatinny system. Um ....... I guess I need a little more guidance here.......

[cshooter]

By the way - Rick. Mine seems to function very well so far. Only got 50 rnds through the pipe. Quite alot more pop than my 223 upper. shoots pretty flat too. And man, hits coyotes hard !