Shimming a scope???

[RangerPete]

Hi Folks,
Any recommendations for the best material to use to shim a scope, and any tips on the best way to go about it?
Many thanks,
Pete.

 

[dgeesaman]

I’ve done a little vertical shimming with Artus type plastic shim material. It held on a mid power springer and left no permanent marks on anything.

My favorite rings generally are Burris Signature and FC No-Limits. No shins required with those.

 

[jusanothajoe]

You can use several different materials, but these work great.

Amazon.com

 

[EmptyTin_Tim]

I agree with the above on just getting adjustable scope rings. I have these on 2 guns and they're great. Can adjust 1mm or so at a time if needed but I have both set up so the rear is higher by one notch so I didn't have to dial far away from mechanical zero on the scope to get close to zero on paper at 25/30 yards.

Amazon.com

 

[jps2486]

I like plastic because it doesn't mar the scope. A polyethylene 1 gallon milk jug is perfect. The material is about 0.015 inch thick.

 

[Crabbypatties]

You can use electrical tape or cut pieces of a can

 

[Leslie]

Most of my airguns are shimmed with soda can aluminum. My concern about plastic is that it might compress over time and cause problems. May or may not be true, but I have more trust in metal shims. I don't use $1,000 scopes so I don't have concerns about marring them. Some of my airguns have really needed shimming, others are usually shimmed to keep them as close to optical zero as possible(where they work their best.) Another thing that I like to do is mount the scope rings close together on the rails before attaching the scope. Cheap rings may have a small variance in their height and mounting them beforehand will make that obvious. I have never tried adjustable mounts because of the cost -- too many guns, too small a budget.

 

[Frank in Fairfield]

Brownell’s sells shims but in the old days we used 35mm negative material.
some old slides laying around the house can be re-purposed.
In a pinch….electrician’s tape..
Some rings come with it already installed to protect the scope..

 

[Revoman]

You may wish to look into this thread....

Never had an idea HOW TRICK these scope rings really are !!! Burris XTR Signature

Good buddy who is thinning his herd of shooting gear gave me a couple sets .... When placing the 1.25" 30mm set onto my vintage .25 WAR Flex it became obvious just how special these ring sets are. Being the inserts Float within the top/bottom ( Main ring & cap ) and the kit comes with 4 various...

www.airgunnation.com

 

[Northwoods22]

For shims I buy 4"x6" brass sheets at the local hobby shop in 5 thousandths of an inch thickness. I cut out my shim with sharp scissors, snip off the 4 sharp corners, and then I clamp a scope ring around an old junker scope or hardwood dowel with the shim to flatten the curled edges from cutting, and to basically pre-form the shim before using it on the actual scope I'm mounting. I've never had a problem with marring or scratching of the scope tube with this method. If 5 thou isn't enough, just double up.

 

[elh0102]

I have also had good results with aluminum can material. As long as you don't need more than around .020" of adjustment, and don't over-tighten, it works fine.

 

[DesertSilver]

I've been using feeler gauges. I usually put a .003 to.005 thick one in and works. I just cut it to length so it sits only in the bottom of the ring.

 

[Michael]

I wouldn’t recommend electrical tape. Prior to using adjustable rings I had great success with a single piece of plastic cut from one those packages that are impossible to open!

 

[rcs9250]

I’ve never shimmed a scope. But doesn’t shimming to add or subtract some moa or mil actually bend the scope tube? Or isn’t it enough to be of concern? I have read of many purest that don’t mount a scope until the rings are lapped to perfection.

 

[boscoebrea]

Perfection for some,not necessary for others,I do not like messy tape,I also use a solid piece of alumin bar to line up rings. Many if not all HW and other brand springers need the 10-20 MOA...Thank you

 

[rcs9250]

Perfection for some,not necessary for others,I do not like messy tape,I also use a solid piece of alumin bar to line up rings. Many if not all HW and other brand springers need the 10-20 degree mounts.

10-20 degrees ? How far you shooting that springer? 600 yards?

 

[DesertSilver]

Perfection for some,not necessary for others,I do not like messy tape,I also use a solid piece of alumin bar to line up rings. Many if not all HW and other brand springers need the 10-20 degree mounts.

10 to 20 MOA not degrees.

 

[boscoebrea]

No wonder I am so far off,LOL.

 

[Ca_Varminter]

Brass shim stock.. Stable, inexpensive, and soft will not mare the scope tubing
In a pinch... aluminum foil works....
This a normal practice for Theoben Rapid MKII....
Almost Always ran out of Scope elevation adjustment!!

 

[RangerPete]

Thanks for all the reply’s guys.

After considering the many options suggested here I agree, adjustable mounts are the answer, but where I live options for those are non existant, so I decided to go with a plastic milk jug.

I chose the plastic because it might be ever so slightly compressable, and my reason for wanting it to compress is as follows…

If you have two flat, level surfaces, I.e. the inside of the rings where the tube will sit, and if they are both perfectly flat and level with each other (in an ideal world) the tube should sit flush and make full contact along both surfaces.
If you raise the height of the back surface by placing a shim onto it, the two surfaces may still each be flat and level, but they will not be the same height anymore. If you now place the scope tube onto the rings, the tube is not going to sit flush or make full contact with either surface. If you shimmed (raised) the back ring, the scope tube should now only be making contact with the two rings on the leading (forward edge) of the ring.

Ideally you want the shim to be triangular in shape, to make contact with and support the full length of the scope tube for the full length of the ring, and ideally you want 4 of these triangles to support the scope tube, top and bottom of each ring.
I chose plastic because I’m hoping it will compress ever so slightly near the forward edge of the rear ring, becomming slightly triangle shaped, but still support the scope tube at the rear where you want it raised.
The scope tube on the front ring, well that dosent get any support but this is not the ideal solution to the problem, that would be adjustable mounts, shimming is an imperfect solution.

I’m not worried about the plastic compressing further over time. Why would it? IF it is going to compress as per my theory above, it will do it while you are applying pressure to it, I.e. when you are tightening the screws. Once you stop tightening the screws it has no reason, or additional applied pressure to compress it any further.

I probably over think everything, but that’s my 2cents worth
Pete.