Rifle Scopes shim a scope?

[super jim]

Just installed a new Bushnell E62440 scope on a DPMS LR.308 flat top. At 100 yards, the point of impact was about 8" low. So I adjusted the elevation to correct. But then I thought, how much more adjustment is left for longer shots...not much. So I shimmed the rear bout .035" betweent he rail and the bottom of the rear ring. That put me about right where I need to be with the crosshairs neutral (in the middle of the adjustment range). But why should I need to shim that much? Is that normal? What could cause this much miss alignment? Is that going to cause a problem?

 

[gdsf2]

Re: shim a scope?

You need a base that adds some 10+ MOA forward cant. Basically a shim but a good one.

 

[kskevin]

Re: shim a scope?

I had a similar issue but the 20MOA base I put on was too much elevation and caused the scope to still shoot about 8" high at 100yd with my 65MOA of adjustment bottomed out. I did some leveling of the base using Devcon and now I have about 12MOA 'down' adjustment and 53MOA of 'up' adjustment. In hindsight, I could have used a 0MOA base and I would have ended up in the same spot but without having to bed the base.

The only cause I can think of it simply the design/machining of the top of the action not being perfectly parallel to the bore. Lesson learned for me to check this before buying a base so I know exactly what is needed next time.

 

[HOGGHEAD]

Re: shim a scope?

Shimming a scope is like putting a band aid on a cut that needs stitches.

You need to determine what the problem is?? And if there is a problem?? And if you need a mount with elevation added then get the proper mount. But shimming is just an accident waiting to happen IMO. Tom.

 

[super jim]

Re: shim a scope?

I don't like the idea of shimming either. The base is an integral part of the upper receiver so it's not adjustable or replaceble. The rings are Burris Extreme 6 hole rings so they should be good. I removed the scope and reinstalled it 2 times just to make sure it was mounted right. Puzzled.