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Originally Posted by nighthawk
Originally Posted by pete53
yes shimming works but i really hate to shim,i would rather get the right mounts for my rifles if i plan on keeping that scope on that rifle for a long time. scope mounts are not that expensive.

Been gritting my teeth but can hold it no longer. If a scope won't zero something is wrong between the scope and the rifle (assuming the scope is good). If you shim it there is still something wrong between the scope and the rifle. Petty little things like that wear on me. Silly I know but I feel much better with things done "right."



Of course something is wrong, if not there would be no need to shim



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FWIW, it's a custom rifle with mounts and rings I can't identify and, given my luck in these things, oddball spacing in the base mount screws. I'm looking for a simple solution versus having to fill and then re-drill and tap screw holes for another type of base. Sometimes, the perfect is the enemy of the good and in this case I'll be satisfied with the good.

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In that case you can go to Brownells (for one) and buy steel shim stock and cut a shim to match the scope base. The idea is to blue shim and have no unsightly gaps or lines between the base and the receiver. Brownells also sells a scope shim kit punched out of steel and blued. At least try to use one decent looking shim rather than a stack of pop can bits.

scope shim kit

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just put a custom picatinny base on this rifle should take care of your problems, i put custom picatinny bases with 10 degree on my number 1`s before anyone made them.


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[quote=erich]A little something I've been playing with.

[Linked Image]

An old Balvar 8 with really clear glass. I use windage adjustable bases or rings and shim for elevation. I call it the "Turret Twisters Nightmare", you'd be surprised at the number of baffled shooters at the range when they notice there are no adjustment knobs on the scope. I've since moved it to a Savage 22-250 with Leupold windage adjustable base, shown are Weaver windage adjustable rings. I use greased hard paper shims(computer paper) they don't continue to compress over time and are easy to insert by just loosening the ring screws.[/quote


And I thought I was the only one to do this....I love those tapers cross hairs...I have one mounted to a rem target master I rebarreled to 17 hm2. Cool setup...

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Originally Posted by cotis
What type of bases are on the receiver? If they are anything "standard" I would seriously look at the Burris Signature rings with the plastic offset inserts. They do a wonderful job of correcting alignment issue of scopes, both vertically and horizontally (or a combination of both!). You can find a combination of plastic offsets that will allow you to keep the scope turret adjustments roughly centered so they aren't running near or at the limit of the internal springs. Plus they don't mark up the scope body and slippage won't be an issue on a .22 Hornet. Just my $0.02...



I had a Savage 99 that ran out of windage. I bought the Burris offset inserts. They fixed the problem. They will correct your elevation problem also

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Another option is to lap the bases. Sounds like the rear one needs to be lower. Depending on how much height difference you need I would remove the bases and wrap the action with 220 or finer grit wet or dry sand paper and stroke the base over the mounting area lightly. Look for full contact and remount to check alignment frequently. This could reduce the need for shims or possibly make them unnecessary. Depending on the type of mount you could also remove material from the top of the base but harder for this not to show although cold blueing will make it not so apparent.

There is a formula for calculating how much the mounting is off but I would have to look it up, it is for iron sights but may adapt to scopes. Or you could shim till the scope is centered and use that as the measurement. But if it takes more than some tape or a single shim I would turn it over to a good gunsmith.


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Paul[/quote]
Originally Posted by greydog
When I have this sort of misalignment, I generally use five-minute epoxy to bed the scope into the rings. If I need to raise the front ring, (and, in this case, it hasd to come up quite a bit) I cut a thin strip of business card which will lie in the front of the front ring. I then wax the scope tube, degrease the bottom half of the rings, mix the epoxy and put some on each ring. Then, put the scope in the rings (don't dawdle!) and snug the tops down (not too tight. just enough to bottom at the rear of the rear ring while the front is supported by the card). Let it set up for a half hour or so then remove the scope and trim off the excess epoxy and there you have it. The bottom halves of the rings will be perfectly aligned with the scope tube and the scope will be sitting in the correct attitude. GD


I use this method with good results as well. I figure that If the scope tube is not straight, at least I’m not stressing it. On the other hand, if I was switching scopes on a rifle or planned to, I would use the precision steel bar method. These are both sound ways of going about this.

Every scope I put on a rifle is glass bedded to the rings with none other than JB weld.

I would check to see if there is shim under the rear base before shimming the front base or ring.

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My dad always taught me, as a rule of thumb .001" worth of shim is ABOUT 1" at 100yds. If your 7" high, you will want atleast .007" of Shim. I believe Pop/Beer can material is appx .010-.012" thick




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Originally Posted by Huntress1956
My dad always taught me, as a rule of thumb .001" worth of shim is ABOUT 1" at 100yds. If your 7" high, you will want atleast .007" of Shim. I believe Pop/Beer can material is appx .010-.012" thick


Just do a similar triangles comparison if you want a better approximation.

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Originally Posted by Tejano
Another option is to lap the bases. Sounds like the rear one needs to be lower. Depending on how much height difference you need I would remove the bases and wrap the action with 220 or finer grit wet or dry sand paper and stroke the base over the mounting area lightly. Look for full contact and remount to check alignment frequently. This could reduce the need for shims or possibly make them unnecessary. Depending on the type of mount you could also remove material from the top of the base but harder for this not to show although cold blueing will make it not so apparent.

There is a formula for calculating how much the mounting is off but I would have to look it up, it is for iron sights but may adapt to scopes. Or you could shim till the scope is centered and use that as the measurement. But if it takes more than some tape or a single shim I would turn it over to a good gunsmith.


You need to be careful with the lapping. Even one thickness of sandpaper increases the radius of curvature of the action. If you fully lap to that radius, when you remove the paper, the base now has a larger radius of curvature than the action. The base will make contact with the action only on a line between the screw holes. Then you will need to epoxy bed the base to the receiver.

The formula for scope shimming is the same as for sights, but you use the distance between the rings instead of the distance between the front and rear sight. As mathman mentioned, similar triangle is the way to think about it.


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Some very good ideas here, but for the love of easy, shim the durn base! Easy.

Guys used to do this for long range shooting ALL the time before 20 and 30 MOA scope bases were available. You might need longer screws, or you might not. This is not just a good solution, it's a great solution. Don't honk the scope rings down super tight yet (which in theory might mark the scope tube, shim the base until you're somewhere in the middle of the scopes adjustment range, then, if you want to be anal, lap the rings (with the scope bases at their new height).

I have done this many times, used beer cans, Devcon, beer cans plus devcon, etc

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Burris Signature Rings with offset inserts. Works great to align scope, holds scope well with hard kickers, won't mar scope either. Return scope to optical center by adjusting cross hairs looking thru scope up against a mirror and "line-bore" looking thru bore and you should be good to go. If you use dual dove tail mounts, the Burris Rings will work with Leupold bases which have a better looking sculptured appearance to me. This is of course if Burris still offers this product. Have used them many times in past with very good results. By using a .030" insert in front and back, you can get up to .060" offset if needed. Several insert sizes to choose from. Oh yeah, I'm not a Gunwriter. Just have run into this more times than I should have.

Last edited by ChuckKY; 07/19/19.
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Aw gee, don't make it complicated.

If there's not a lot of shimming to do, and it's not a loudenboomer, a pop can and scissors are your friend.

1. To get an idea of HOW MUCH shim, measure the distance between rings, get out your calculator, divide 100 yards (3600 inches) by your rings. You want seven inches (thats 14 inches at 100) PLUS whatever it takes to get centered, so you should spin the turret to see what your total adjustment is. Half of THAT gets you what you need to hit optical center, which is what you want.

2. You need to decide whether to shim INSIDE the ring, or UNDER the front base. It might be best to get a couple of slightly-longer base screws and shim underneath, because that doesn't mess with the inside diameter. If your total rise is more than one turn of the screw and you have less than three turns, you definitely need to get some longer screws to use all the thread you can.

3. In all cases, it's good to at least CHECK ring alignment and whether or not lapping is needed. If the alignment is bad, I'd shim the bases with longer screws, then lap it good. If alignment is pretty good and you don't need a mess of shims, just plopping a shim about 1/2 wide on the centerline should work okay just as long as you don't crank the ring screws too hard.

I have done:

1. Shim rings, with a skin-coat of JB Weld as an adhesive, then lapped that. You'll need some kind of release agent on either the scope, lapping bar, or whatever straight round stock you use. I also ruff up the inside of the lower ring to give some "grab,"
2. Shim base, again using JB as a gap filler. Lap rings after. If you put JB or some other good epoxy on both rings, you might not need to lap at all. There's also some Loctite green stuff for bedding, Mic McPherson wrote about that. Works for bases, I don't think he's used it on rings, and by the way, he's a huge fan of the Burris setup.


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