Shim rear of scope or buy 20 MOA rail

FatCatsDad

FatCatsDad

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Is shimming the rear scope ring to gain more elevation adjustment a half ass way to do things or acceptable ?

Is the proper way to do this buying a new 20 MOA rail and a set of rings.

Rail and rings would be over $200 and I spent $80 on a set of Talley integrated base/rings.

I can't seem to get the POI high enough..

Currently just bore sighting with a laser and even ifvthe laser is off a bit, I'm maxed out on elevation and still low.

I did 2 others with the laser and they were fine.

I did it outside this morning while it was still dark enough aiming at a birdhouse about 75 yards away.

It's a bushnell 3500 scope.
 
Front ring is fixed, scope solidly in place. Rear ring is shimmed, raising it. Scope is being tweaked.
Easiest solution is to use Burris Signature rings with eccentric inserts. Scope is at rest with whatever elevation is desired.
 
I suspect what you propose could be done - in theory, your standard factory rings ought to be sort of parallel with your rifle bore - if you put a shim under the scope body at the rear ring, that will tilt that scope body - meaning only an edge of the front ring will bear on the scope body - so you really need a thin wedge shaped shim for front ring, then thicker wedge shaped shim for rear ring - is probable that the ring caps will remain parallel, so they might need to be "lapped" to that new scope body angle, if standard rings and bases are used. About same issue if you put shim under scope bases - you are tilting the assembly - most definitely can be done - use metal shim to get "tilt" that you want and then fill "gap" with epoxy - in effect "bed" the bases to receiver, but not parallel to it - whereas typical factory stuff wants to have it sort of parallel to the rifle bore. Is the "magic" of those 20 or 30 MOA long bases - their top surface is not parallel with their bottom surface - usually installed so their thin end is to the front.
 
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Swap ring positions - OP said he is using Talley integrated base / ring units - usually different hole spacing between front bases versus rear bases - so I doubt that he can swap those around.

He might want to try to reverse each front to back, to see if they have a cant to them? Many scopes no longer made long enough to do that, might no longer fit that scope to "backwards" rings - and still get adequate eye relief, though.
 
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I mean, I've done it before with a strip of pop can aluminum but I'm not sure if that's going to give you any meaningful consistency. Worth a shot, worst case it doesn't help, you haven't permanently modified anything.

What rifle are the Talley's mounted on?
 
That scope has 14 mrad (48MOA) of elevation. How far out are you shooting to require a 20MOA rail?

Something is not right if you are aiming at 75 yards and you are out of elevation.
 
Paul_T said:
That scope has 14 mrad (48MOA) of elevation. How far out are you shooting to require a 20MOA rail?

Something is not right if you are aiming at 75 yards and you are out of elevation.
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After much screwing around ive determined the scope is NFG.
I mounted it on a Ruger M77 in Ruger rings and got the same result, and just to be safe on a Model 7 in Leupold PRW rings, same result.

I'm glad I took the time to try it on a couple if other setups.

I gave it to my youngest granddaughter to play pirates with. (Pirates of the Caribbean was on TV last night)

Now it's off to the EE to find a replacement.

I may put my dislike aside and buy a Vortex Crossfire

It's just for a knock about short 13" Scorpio .22
 
Before you condemn your scope, and/or spend time and dollars on a new mount, i suggest you actually shoot the rifle. Your boresighter may have worked for other rifles, but you shouldnt assume it works for all rifles. So, for the cost of a few cartridges, you will have much better insight into the matter.
 
FatCatsDad said:
Is shimming the rear scope ring to gain more elevation adjustment a half ass way to do things or acceptable ?

Is the proper way to do this buying a new 20 MOA rail and a set of rings.

Rail and rings would be over $200 and I spent $80 on a set of Talley integrated base/rings.

I can't seem to get the POI high enough..

Currently just bore sighting with a laser and even ifvthe laser is off a bit, I'm maxed out on elevation and still low.

I did 2 others with the laser and they were fine.

I did it outside this morning while it was still dark enough aiming at a birdhouse about 75 yards away.

It's a bushnell 3500 scope.
Click to expand...
a 20MOA rail is one way to go. Another would be Burris rings with the right inserts. You can do +10 in the rear and -10 in the front, or +20 in the rear and 0 in the front ... etc.

As cosmic says above though, I'd start by boresighting (by eye - not with the laser) it at 50m to get on paper at 100, then see what it can do just the way it is.

Good luck
 
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