Scope Shimming ?

Forums Optics, Scopes, Rings, & Mounts Scope Shimming ?

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    bigbobbybeef
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    I have a FX crown with a hawke sidewinder and FX no limit rings has anyone ever shimmed a scope to make it more to the right or left up and down no problem but i am 1/2 spin on the turret for full right if so what do you shim it with I have moved the mounts front back and spun them 180 degrees still shoots to the right ?

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    Gettsgunner
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    Never ran into this problem . Shimmed scopes for elevation but never windage.  Anxious to know what the experts answer is.  

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    bubblerboy64
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    Check your rings to see that they are seated on the dove tail or P rail correctly 

    If so you might rotate the barrel liner .   I think the disadvantage to the liners is that they seem to be sensitive to their position relative to the barrel and the nut holding them in place.  

    Finally the scope could be the problem . Try another scope

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    survivor45
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    Go buy a cheap set of feeler gauges. Like from Harbor Fright. Make your shims from them. 
    That’s my only suggestion. I’ve never shimmed a scope before. So no help there.  
     

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    bigbobbybeef
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    bubblerboy64 i dont think you rotate it on the crown i pulled the barrel and the brass piece has a notch in it to go back into the same spot i had thought about that unless it comes apart further its a brand new hawke i was thinking the rings could be off a couple of thousands or the picatinny rail could be off a couple of thousands and that would throw it off. I have some stainless shimstock i think its .004 thickness.

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    oldspook
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    Chairgun has a function which can help you calculate how much shim you need.   After you have made sure that everything else is locking up correctly, set your turrets to 0/0 and shoot a group on a large target at 25 yards.  Measure the distance between your aim point and the POI.  You will need to add enough shim to the LEFT SIDE of the FRONT RING (you said your turret was nearly full right so you need to go right).  If you measure the distance between your rings you can calculate the thickness you need for that shim.  First measure from the start of the first ring to the start of the second ring.  That is the distance between the rings. 

    1) Divide the distance between the rings INTO 25 yards (or your target distance).  Use this number in the next step.

    2) Divide the distance between your POI and your aim point by the number you got in step 1.

    This result is the thickness of the shim you need to move your POI to zero.

    So here is an example.

    Distance between rings is 3.5"

    Distance between POI and aim point is 22"

    Range is 30 yards (30*36=1080)

    Step 1:  So 1080/3.5 = 308.6

    Step 2: 22/308.6 = 0.0713"

    Your shim needs to be 0.0713" thick.  In your case it needs to be placed on the front ring, left side.

     

    Hope that helps.

    • This reply was modified 8 months ago by oldspook.
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    Skip-in-WV
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    I shimmed scopes for years with a piece of Coke can and plastic from a "bubble" wrap. Here is something to think about though. If you shim the you've raised one end but not the other. This, in my mind puts extra stress on the scope tube when both mounts are tight. IMHO I think adjustable mount are a better option. I now use the FX No Limit mounts. No extra stress on the scope tube, and the mount can be adjusted until the elevation turret is in the middle of rotation at whatever distance you decide to zero.

    • This reply was modified 8 months ago by Skip-in-WV.
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    biohazardman
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    bigbobbybeef

    bubblerboy64 i dont think you rotate it on the crown i pulled the barrel and the brass piece has a notch in it to go back into the same spot i had thought about that unless it comes apart further its a brand new hawke i was thinking the rings could be off a couple of thousands or the picatinny rail could be off a couple of thousands and that would throw it off. I have some stainless shimstock i think its .004 thickness.

    If the front of the barrel has flats on it it has a liner inside.  I have used plastic from clamshell wrapping and aluminum from aluminum cans for shims in the past.  I have also shimmed the rings at their mounting points rather than inside the rings.

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    dangmistagen
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    I cut a piece off my aluminum mini blinds to shim my scope and it worked great.

     

     

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    bigbobbybeef
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    I am using no limits from FX but you can only adjust up and down not left to right am i correct ? my only problem is left to right .

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    biohazardman
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    bigbobbybeef

    I am using no limits from FX but you can only adjust up and down not left to right am i correct ? my only problem is left to right .

    You can shim left or right by using a small piece of aluminum cut from a can, regular scissors werq for the cut, in the dovetail where the rings reside on the rifle.

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    Airgun-hobbyist
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    A couple things to consider before shimming the side of the dovetail mounting clamps…

    With a set of calipers,  can you take some measurements of the slotted portions of the mounts to see if the parts can be rearranged to get the shift you are looking for there?  Also, can you place a shim in the slots to make your adjustment that way?  

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    bigbobbybeef
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    I have switched the mounts front to back turned one way then the other mount the other the shift is still the same i figure its in the picatinny or the mounts which arent cheap i am gonna try tomorow putting a shim inside the slot one side on the front other side on the back and see if it works biohazardman that sounds like a good idea i have other mounts that i could try but they dont have the height adjustment to miiss the mag.

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    Airgun-hobbyist
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    Trying the other mounts would verify the rail being off.  Isn't that ST-X inner barrel liner removable, similar to the Impact's?  Before going into a bunch of extra testing and replacing, I'd try pulling the liner cleaning the barrel tube's inner bore, the ST-X liner and greasng the o-rings.  I know the first time I took mine apart it was a chore and needed a good cleaning, inspection, and thoughtful assembly.  Ernest Rowe told me he puts a couple wraps of tape on either side of each o-ring on the liner so they stay in one spot on the way into the barrel tube.  This helps keep them in place tremendously.  My poi shifted and was more consistent  after doing these things.

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    leadfoot
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    You could get a set of Burris Signature rings with the offset inserts. If you orient the wider part of the .020 offsets to the right in the back and the wider side to the left in front you will get .040" of adjustment. The "offset inserts" come in pairs of .005, .010 and .020 so you can dial in what you need. If you need it mounted higher you can certainly get some 1/2" risers to fit under the mounts, if the "high" version of the mounts are not  high enough for you.

    Doing it this way will not stress you scope tube, is totally reliable, and is a very adjustable platform. If I ever need some of these I usually get them at Brownells, however if you need the 30mm or 34mm variety you may need to order them from Burris. Hope this helps.

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    bandg
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    leadfoot

    You could get a set of Burris Signature rings with the offset inserts. If you orient the wider part of the .020 offsets to the right in the back and the wider side to the left in front you will get .040" of adjustment. The "offset inserts" come in pairs of .005, .010 and .020 so you can dial in what you need. If you need it mounted higher you can certainly get some 1/2" risers to fit under the mounts, if the "high" version of the mounts are not  high enough for you.

    Doing it this way will not stress you scope tube, is totally reliable, and is a very adjustable platform. If I ever need some of these I usually get them at Brownells, however if you need the 30mm or 34mm variety you may need to order them from Burris. Hope this helps.

    Very good advice.  The Burris rings are excellent if they can be found for the application.  The SportsMatch fully adjustable rings are another option-not cheap but they work very well and do provide both elevation and windage adjustment.  Any shim, whether in the ring or the base, can possibly put stress loads on the scope that aren't desired.  Many people seem to be fine with shimming scopes and it may be acceptable with no damage at all.  I never have and still do not do it.  

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    Doug-T
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    Make sure the shim is on the solid part of the mount clamp.  Putting it on the separate clamp side won't do anything.

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    bigbobbybeef
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    Thats what i did my shim was .004 and they fit exactly just a tad snug so i put them on oppisite sides and slid the mounts in tomorrow ican try it and see what it did.

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    leadfoot
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    Just a suggestion, don't over tighten the rings. You know the old saying… two objects can't occupy the same space at the same time.

    I can understand how placing a shim on top of the bottom ring saddle would raise the scope up. To "account" for the displaced volume _and still not crush the scope tube_ you would not tighten the cap all the way down. But there is no "give" when trying to adjust side to side. In a battle for room, the looser will be the tube. 

    I could be wrong. Please let us know how that works out.

    • This reply was modified 8 months ago by leadfoot.
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    Bigragu
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    leadfoot

    Just a suggestion, don't over tighten the rings. You know the old saying… two objects can't occupy the same space at the same time.

    I can understand how placing a shim on top of the bottom ring saddle would raise the scope up. To "account" for the displaced volume _and still not crush the scope tube_ you would not tighten the cap all the way down. But there is no "give" when trying to adjust side to side. In a battle for room, the looser will be the tube. 

    I could be wrong. Please let us know how that works out.

    He’s putting the shims on the FX no limit mounts, where they clamp to the scope rail, not within the scope rings, or saddles, themselves. 

     

    Hey, BBB, by chance before you mounted the new scope, did you check to make sure it was optically centered? My Athlon Helos, brand new out of the box I needed to center optically myself, even though the instructions said they came centered from the factory.

     

    Brother, you gotta invest in this tool. Makes life easy.

     

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