HOW TO SHIM SCOPE MOUNTS ON RIFLE - The HuntingPA.com Outdoor Community

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post #1 of 20 (permalink) Old 07-22-2011, 10:56 PM Thread Starter
MrC
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HOW TO SHIM SCOPE MOUNTS ON RIFLE

Anyone out there have any experience shimming a scope mount on a Mauser action custom rifle? I sent my Bushnell scope back to have it checked out and they said that the scope was overadjusted/shim mounts on the repair order. My guess would be to start by laying a straight edge across both mounts to see if they line up properly. Any guidance on procedure and/or assistance on the allocation of some shims would be appreciated. I've used shims in automotive circles before. But, this is a new one for me. MrC

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post #2 of 20 (permalink) Old 07-22-2011, 11:36 PM
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Re: HOW TO SHIM SCOPE MOUNTS ON RIFLE

Ok, this is really easy, but difficult to put into words.

slowly move your scope to a centered position, move it up down and count the clicks between all up and all down. Move to 1/2 of that distance/clicks. then it is elevation centered.
Then do a centering on the windage; all right --all left and count those clicks; then put it at 1/2 that number of clicks.

The internal adjustments on your scope are now centered.

Take it to the range and shoot at a large 3'x3' target at say 50 yards. shoot 5 shots and see how high or low the group is. For this say the group is 15 inches high at 50 yards.
Now it is a simple ratio of the distance and the amount high (or low) all in inches. in the example the 50 yards is 1800 inches so the ratio on a high group is 15"/1800" or .00835.
We apply that ratio to the distance between the front and the rear scope bases, assume that distance is 6 inches.

6" time 15/1800= .05inches If the group is high you will need to raise the front mount UP .05 inches. If the group is low then you need raise the REAR mount that ammount.

Just buy some shims (Burris #625051) and place a .05 thick shim under the front mount (between the bottom of the mount and the receiver ring, tighten base screws and you are there.

Burris Scope Base Shims http://www.midwayusa.com/viewProduct...tNumber=585609
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post #3 of 20 (permalink) Old 07-22-2011, 11:47 PM
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Re: HOW TO SHIM SCOPE MOUNTS ON RIFLE

Too late

Bob Seger,till it shines.
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post #4 of 20 (permalink) Old 07-23-2011, 12:16 AM
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Re: HOW TO SHIM SCOPE MOUNTS ON RIFLE

Generally you can't shim right to left or windage. You need to file the rear mount on one side or the other; not to difficult IF you have weaver style mounts.

Should have mentioned, you can but mounts that are windage adjustable.
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post #5 of 20 (permalink) Old 07-23-2011, 01:10 AM
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Re: HOW TO SHIM SCOPE MOUNTS ON RIFLE

Quote:
Originally Posted by MrC
My guess would be to start by laying a straight edge across both mounts to see if they line up properly. Any guidance on procedure and/or assistance on the allocation of some shims would be appreciated.

MrC
I suggest you buy a set of Burris Signature rings with the inserts. Remember, more scope problem are due to mounting than the scope itself. Shimming nine times out of ten bends the snot out of the scope tube.

First optically center the reticle using a mirror. Start with the zero MOA inserts and using a bore sighter or the eyeball method see how the scope aligns. If its way off use the offset inserts to correct it and/or get it close. You should have plenty of adjustment to zero the rifle.

Burris Signature rings

Inserts

Bill
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post #6 of 20 (permalink) Old 07-23-2011, 09:08 AM
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Re: HOW TO SHIM SCOPE MOUNTS ON RIFLE

MrC [/quote]

(I suggest you buy a set of Burris Signature rings with the inserts. Remember, more scope problem are due to mounting than the scope itself. Shimming nine times out of ten bends the snot out of the scope tube.)

Excellent advise.

benchrest
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post #7 of 20 (permalink) Old 07-23-2011, 05:55 PM Thread Starter
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Re: HOW TO SHIM SCOPE MOUNTS ON RIFLE

Thanks Harry. Shims are the cheaper way to go and could work in my app. if the elevation is the only issue. But, since I'm not on a shoestring budget, I ordered a set of Burris Signature Zee rings and a kit of concentrics in .005, .010 and .020 last night. Total was like $80.00 I took a closer look at my no name aluminum rings and the contact area at the tube was not satisfactory to me. So, on with the Burris'.

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post #8 of 20 (permalink) Old 07-23-2011, 06:05 PM Thread Starter
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Re: HOW TO SHIM SCOPE MOUNTS ON RIFLE

Thanks for your opinion Bill. Good to here we're on the same page. I already have a 1 inch pair of Signature Zee's on the way in medium hieght, polished blue along with a 3 piece concentric kit. Most well known suppliers are out of the matte. Did some research last night. Haven't heard anything but good about them.

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post #9 of 20 (permalink) Old 07-23-2011, 06:12 PM Thread Starter
MrC
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Re: HOW TO SHIM SCOPE MOUNTS ON RIFLE

Hey Bill. Sound advice. Thanks. Bushnell re-centered the reticle when the checked it over last week. Those guys are fast! Mailed and back to my door in like 17 days. MrC

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post #10 of 20 (permalink) Old 07-23-2011, 06:50 PM
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Re: HOW TO SHIM SCOPE MOUNTS ON RIFLE

I have a precision machined piece of 1" stainless round stock to check the alignment of the mounts( rings). Been doing this for over 30 years and have rarely found many out of alignment, but when I did, I always used a piece of film negative. Works great, and doesn't harm the scope or rings. All that said, s good gunsmith will now lap rings for you to make a much better fit, although if it's an elevation issue shimming is still required.

I gotta go melt my butter!
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