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Scope shimming

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bl30

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I've never needed to shim a scope before, but having taken a punt on a second hand scope I find I don't have enough vertical adjustment.
I have some aluminium beer can to use for the shim but was wondering do people place it between scope and mount or mount and gun?
It's going on a Daisy 880 pumper so recoil isn't a concern.
 
I've shimmed scopes using slivers of paper, which most would think is a soft material, but I spent a long time in the print supply industry & can tell you that paper is actually quite hard in that it does not compress.
And it's a lot easier to cut a little oblong of paper than metal !
 
Shimming will cause uneven stresses in the scope tube so I would avoid it if possible. It's far better, bar the cost, to use adjustable mounts if there is a problem with alignment between barrel and dovetail. Try the usual, ie swap mounts around etc and is the barrel bent or otherwise misaligned but adjustable mounts will sort the problem.
 
No no no no no

Let's say you jack the arse end up so it's now pointing down and the muzzle is raised, you're now clamping the front ring with the forward edge and not a flat surface, its a point contact which will at worse dent the tube, at best put a bentldinf stress on it.

Something else is up like the barrel is bent, rails are loose or bent or the rings are just crap.
 
If a scope needs to be shimmed, it really should be done with a matched pair of shims for the front and the rear. . This will prevent damage to the scope. . Try these:

www.ebay.co.uk

Hawke 30mm Scope Shim 25 MOA Mount Insert For Air Rifle Rimfire | eBay UK

Adds 25 MOA (Minutes Of Angle) of elevation adjustment to rifle scopes in order to give more adjustment, ideal for uses where there isn't enough adjustment on the scope to zero in and for long range shooting. Designed for use with Hawke Match Mounts but also suitable for some other brands of...
www.ebay.co.uk
 
I’ve only ever shimmed a scope evenly on both rings to lift it slightly if clearance to the cylinder/action is a bit tight. For that, I’ve used pieces of fizzy drinks bottle.

Shimming just one ring, particularly with double screw mounts, risks crimping and bending the tube of the scope.
 
Wing Commander said:
If a scope needs to be shimmed, it really should be done with a matched pair of shims for the front and the rear. . This will prevent damage to the scope. . Try these:

www.ebay.co.uk

Hawke 30mm Scope Shim 25 MOA Mount Insert For Air Rifle Rimfire | eBay UK

Adds 25 MOA (Minutes Of Angle) of elevation adjustment to rifle scopes in order to give more adjustment, ideal for uses where there isn't enough adjustment on the scope to zero in and for long range shooting. Designed for use with Hawke Match Mounts but also suitable for some other brands of...
www.ebay.co.uk
Click to expand...

The only problem there WC is if you shim the scope both front & rear it will achieve nothing as the angle of the dangle will remain unchanged.
 
Old film negative was a favourite material for scope shimming and if you have insufficient vertical elevation you will need to shim the bottom cradle of the rear mount to cause the front of the scope to be lowered in reation to the barrel.
You can also use folded alumium kitchen foil to shim the rear mount and there is or used to be an article on BSA's website showing you how to do it. It is folded in such a way to minimise the risk of marking/damaging the scope tube,
I wouldn't shim an expensive scope there's a risk of marking, distorting or even slightly crimping the scope tube if it requires a lot of shimming but as it's going on a Daisy 880 pump i can't imagine it's an expensive scope.
For an expensive scope i'd use either adjustable mounts or a scope elevation compensation mount.
The main reason for running out of elevation adjustment is barrel droop where the barrel points slightly downwards in relation to the breach/cylinder/body tube.
It's more common with break barrel guns than fixed barrel guns.
 
Last edited:
2506sendero said:
The only problem there WC is if you shim the scope both front & rear it will achieve nothing as the angle of the dangle will remain unchanged.
Click to expand...
That's a very reasonable assumption but the shims are engineered to give 30MOA elevation while the scope sits perfectly flat on them.
IE.. the front one is different to the rear one.
 
2506sendero said:
I stand corrected WC :)
Click to expand...
If you're shimming both mount cradles and the front and rear shims are of different thickness i.e. the shim(s) in the rear mount cradle are thicker than the front cradle shim(s) or vice versa the scope tube will be out of alignment in relation to the mounts.
This why on adjustable mounts each mount can be adjusted independantly so that the scope tube still sits perfecltly flat/square in each of the mount cradles.
On a one piece droop compensation mount the mount is made so that the scope is tilted fractionally downwards but still sits flat/square in both the front and rear clamps/cradles.
 
For those who have commented that shimming one mount will put the scope under stress etc. Technically, you are of course right, but practically, when the shim is measured in thousandths of an inch, the actual effect will be vanishingly small to non existent.
 
Just buy some proper scope rings, I highly recommend eagle vision, they have a range of brilliant height adjustable scopes.
 
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