First time I've run into this....shimming a scope base?

Hitzy

Hitzy

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Been messing around trying to make the ugliest shooter I could take to the camp this fall.....cheapest ugliest gun that can shoot the snot off a butterfly at 200m.
Everyone there has the nice stuff, Sako's, Weatherby's, Browning's, real nice guns, with nice scopes, but they are all getting up there and would rather talk about their gear then actually get out and hunt lol.
So I'm about $275 into this dog, one of those $125 "professional sporter" '96 actions in 6.5x55 from Tradex, already had a flaking sporter stock, got all the little bits from the local smith for peanuts, and using a niceish bent bolt from another rifle....topped with a NOS Bushnell Legend in 3-9.
Everything checked out, off to the range and I'm out of vertical adjustment... Still about 8" low at 100m. I should have known when I installed the rear base and the screws went through the receiver and had to be filed down about 1/16". When they removed the charger ears, I guess they took the rear bridge down with it....meh.
Good news is it shoots clover leafs with the worst factory ammo I have ever seen, so I know it's a keeper. Should I shim the base, or do the Burris offset route... Or something else?
Shimming and the Burris inserts don't seem like most durable solutions... I dunno though, I just like metal on metal, so any solution would be great. The scope has lots of adjustment, I forget the specs but it's 60 or 80 moa...so the rear base is pretty low.
 
Shimming and the Burris Signature rings would work well... and about the cheapest way to a solid fix.
 
If you are using weaver bases, you may be able to find the next thickness, and use it. I ran into an auction a few years ago where the place was going out of business. Selling a box full of weaver bases. Think I paid $40 bucks for the box. It had some old junk in it, but had about 20 sets of new, various base sizes still in the package. What I found was that many of the bases had exactly the same radius. (Some were flat). Many had the same hole pattern. (Distance between holes). The only difference with many was the thickness of the base. This box has saved me on numerous occasions.
 
Read somewhere to use pop cans. Its metal and thin enough to stack a few until you get to your desired rear base height.
 
I recently ran into the same problem on a rifle, I used shims that I made from a piece of steel strapping I had. Its blued and is not noticeable at all, and fixed the scope bases right up were they needed to be.
 
Popcan material works well, plastic from the base or ring packages works well as well(same material as comercialy available shims).
Have had to do both before on customer guns. When there is no point in charging someone $90 for a set of sig zee rings with 10moa inserts. better on a cheap gun than expencive rings and insets. Also depends on how far off the scope is from centre. Generaly shims will bring it in far enough for a hunting rifle.
 
Aries- said:
Popcan material works well, plastic from the base or ring packages works well as well(same material as comercialy available shims).
Have had to do both before on customer guns. When there is no point in charging someone $90 for a set of sig zee rings with 10moa inserts. better on a cheap gun than expencive rings and insets. Also depends on how far off the scope is from centre. Generaly shims will bring it in far enough for a hunting rifle.
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I'm about 8" low at 100m at full adjustment, I'd be fine with 8" of adjustment left over at 100m... so I need to shim like 16moa.
I'll give it a go with some plastic, I think it will take a lot of pop can shims to make that up...lol
 
Pop cans tend to around .004". The no math rule of thumb for typical ring spacing is .001 per MOA. I wouldn't use plastic or anything compressable for shims.

Something to consider when shimming is that if the scope ran out of adjustment its because the rings are out of alignment. When you tighten the rings down the scope tube has to flex enough to make up the difference, so when you shim you don't want to just do enough to sight in, you want enough to bring everything into alignment. Insert rings are the easy way, shimming and lapping work too. Someone mentioned the slightly different thicknesses of different Weaver bases, if you have access to a dealer that will let you open every bag and a caliper it is probably the "real" fix. There were a bunch of Vanguards affected a few years ago, and we got good at it.
 
Years ago I took a 93 Mauser to a gunsmith to have bases mounted. He wasn't a very good gunsmith because the front base was so low I noticed it as soon as I put a scope on. I used four layers of 12 thou aluminum to shim the base and that rifle has shot great ever since.
 
Hitzy said:
I'm about 8" low at 100m at full adjustment, I'd be fine with 8" of adjustment left over at 100m... so I need to shim like 16moa.
I'll give it a go with some plastic, I think it will take a lot of pop can shims to make that up...lol
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Can be a problem with old Mauser actions, if they have been sporterized, the gunsmith that did it may have taken to much off the rear or front mounting surface, (or it was like that from the factory, or the capturing country ground to much off when removing the crooked pigeon from the front mounting surface.

other stuff you can do is likely goto princess auto and find a package of shim stock. it will be brass, or plastic. the plastic works just fine, it wont compress much, and if it does, tighten up a bit more. CNC machinists use it all the time for aligning Fixtures to within microns of flat, and it will stay there while hogging out huge amounts of material.
 
Lee Valley sells brass shim stock. You may have to buy enough for several lifetimes, but you'll always have friends if you have brass to spare.
 
robin2y said:
Make a bit of a pad with j-B weld?
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lots of great advice .. I really like Burris Signature rings ... but I have had some success using acraglass when front and rear ring heights were different. Something like this .... first mount the front base and bottom ring section that you currently have to the action ... then connect the rear ring and base securely and mount the ring portion loosely on the rear scope tube - do not mount the rear base to the action. Then set the scope in the previously mounted front ring half and snug down the top ring half with the scope positioned appropriately for eye relief.
Move the rear base/ring on the scope tube for/aft so that it is approximately where it would be mounted on the action and then tighten the rear ring to secure to the scope tube. With the scope mounted securely only to the front ring -- the rear will (presumably since too much was ground from the rear of the action) be suspended/floating and the rear base will now show a gap between it and the action ... You want to fill that gap with devcon/JB/Acraglass etc ..

so ... in the past I have used wax on the action (plugged the screw holes in the action and base with plasticine) and roughed up the underside of the base so that the devcon adheres to the base... build a little dam around the mounting location on the action and drop the scope back into the front ring half and tighten it. you can drill out the devcon for the screws later. go slow as obviously the devcon pad will be thin. Surprisingly durable and stress free scope mounting. I can't say how much closer to zero you will be - depends on the front base of course...but probably a lot closer than you are
 
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