Shimming a scope with pieces of soda can.?

[bandg]

Scopes can easily be damaged even without shimming if scope rings aren't lapped wjenever needed even when using expensive rings.

Over the last 50 years I have seen many scopes with ring marks or damage. The odd thing is I have mounted hundreds of scopes. When young I used the cheapest I could buy and considered myself lucky to get that. I have shimmed a bunch of scopes also because that’s all I could do. Anyway I have never had one scope with ring marks. Is tightening everything even a key? Keeping all the ring gaps equal instead of cranking down on on side or one ring. I don’t know. I had some heavy recoiling contender pistols in rifle calibers and could not leave anything loose. No lessons hear, just wonder.

To me, this may be the key issue and it doesn't in any way seem to be something one can "calibrate". Shimming would by necessity seem to decrease overall surface area contact with the upper part of a ring that is shimmed below and both upper and lower parts of the other ring. How much does one tighten to avoid movement? Can it work? Absolutely. But I also have seen ring damage on scopes that weren't in shimmed rings. So shimming is not something that I want to do. Others may do so successfully. If it works for you then by all means do it.

 

[Saltlake58]

I think we are all more or less in agreement.

Shimming isn't the best idea, but it works. Having done it, seeing how it worked on a cheap, crappy scope and made it usable, I know it works. (Scope was a BSA 6-24x40 I bought on a Black Friday sale for something like $65 a few years ago. Vertical adjustment was so limited, I couldn't get past about 30 or 40 yards before ran out of adjustments!)

Odoyle is also right, Damaging your scope by shimming might happen, While damage isn't guaranteed, best to be very careful. OldSparky, I think you hit it on the head. just be careful how you tighten the rings, use the old star pattern of alternating a few twists on one, go diagonal to the next screw, a couple turns, diagonal to the next until it's reasonably tight. Don't over tighten.

In my opinion, If you need to shim more than a soda or milk bottle thickness (thanks for that information JPS2486, very helpful), you need adjustable rings. That's just my opinion, worth what you paid for it!

Going through the formalities of lapping, leveling, careful tightening, and all proper scope mounting techniques is definitely best. Sadly, I don't have lapping tools, nor the inch pound torque drivers needed to go through the formalities. I think most of us mounting scopes are in that boat. With current precision machining that's in use, not sure lapping is as important as it was 10 or 20 years ago, but still probably the best route. As for tightening, my rule of thumb is to go till it's tight enough to stop the scope from turning, and not much further. over tightening is as bad as over shimming if you get my drift.

I guess I'm kinda like OldSparky, I consider myself lucky to get equipment sometimes. Good equipment is a real luxury, so sometimes I just have to do without. While I hope I never need to shim again, I probably will, but with very careful tightening of the rings to prevent damage.

Very good discussion!

 

[Odoyle]

I like to use the B Square AA elevation and windage adjustable rings on all my older guns they were the bees knees 10 years ago even on mid power springers. PERFECT PERFECT PERGECT optical centered 100% no matter what and how crappy the machining or calibration gun rail or droop or barrel pointy to one side. They are sold by Sun Optics since B Square owner DAN sold the business that changed its name. So much for my LIFETIME WARRANTY windage and adjustable B Square AA MOUNTS!!!. 

The Burris Signature rings with posalign rotating shim nserts were my second fave nut a real birch to adjust. Had to always dismount both front and rear scope rings.

Good news these particular 2 types of rings don't ruin the scope tubes.

 

[Parrotculler]

I agree adjustable rings or lapping are best. IF done properly, meaning without stressing the scope.

But I use cheapo rings only and have never had any issue with shimming. Again, as long as the scope is not stressed/bent/crushed. This can easily be achieved by:

1. Using soft shims only.

I prefer strips of double coated tape. For example, 3 in the rear ring and one in the front ring, against barrel droop. In case of left or right adjustment, shim the rings on the rail with plastic from a milk jug -- always in combination with double sided tape in both rings. The tape provides cushion plus fixes the scope, which enables the second condition:

2. Never overtightening

No more torque than enabled by holding your allen key between thumb and index finger. The screws should be fixed with a drop of blue threadlocker, not by tightening.

This aside, the niftiest option against barrel droop is the adjustable rail on some guns.Check out the Kral Empire.

 

[Pysiths]

35mm camera film if you can find it. damn, I'm old.