Modifying Scope base for cant

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  • rtse4me

    Active Member
    Apr 12, 2013
    298
    Howard County
    I have a couple Sako rifles with their Optilock bases and rings. I would like around 25moa of cant. I know DIP makes a 25moa picatinny rail but they use set screws to hold the rail in place. Sako's are not tapped.
    So I was thinking of just shimming the rear base between the ring and base like .025".
    Would this work? Seems like a easy way to get the cant I need.
     

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    DavidA

    The Master of Disaster
    Dec 6, 2013
    371
    Annapolis
    I have a couple Sako rifles with their Optilock bases and rings. I would like around 25moa of cant. I know DIP makes a 25moa picatinny rail but they use set screws to hold the rail in place. Sako's are not tapped.

    So I was thinking of just shimming the rear base between the ring and base like .025".

    Would this work? Seems like a easy way to get the cant I need.



    Yes it will work just make sure shim set across entire contact areas. If not base can move



    Sent from my iPhone using Tapatalk
     

    atblis

    Ultimate Member
    May 23, 2010
    2,011
    Depending on what you're trying to achieve, buying a scope with a larger amount of adjustment might be an option. The Sightron SIII LRs have something like 120 MOA of adjustment.
     

    Pinecone

    Ultimate Member
    MDS Supporter
    Feb 4, 2013
    28,175
    If you just shim one ring, with a flat shim, the inner ring surfaces with not be parallel.

    You need to shim both front and rear with properly tapered shims.
     

    rtse4me

    Active Member
    Apr 12, 2013
    298
    Howard County
    If you just shim one ring, with a flat shim, the inner ring surfaces with not be parallel.

    You need to shim both front and rear with properly tapered shims.
    Thanks,that makes sense both front and rear rings need to be canted. Figured it wouldn't be an easy fix. I do have access to a small mill but have limited experience. Will have to do some research.

    The other idea I had is to get a DIP picatinny rail and replace the standard set screws with brass set screws so it wouldn't mar the receiver.
    Wish some would make a rail that would tighten like the Optilock bases do
     

    KRC

    Active Member
    Sep 30, 2018
    615
    Cecil County MD
    Shimmed Bases

    I have shimmed one scope base (~.025" or .030" as I recall) and not the other with no issues with not angling the other base ("ghetto MOA bases"). It worked perfectly and enabled me to use the scope for long distance shooting.

    It would be best to use a piece of properly sized round stock (Brownell's?) and lapping compound to lap both rings after shimming, but I've found this was not required, at least the time I did it. Some scope rings come with sticky fabric strips or some other material which also helps with alignment.

    How much of a lift do you need?
     

    1time

    Ultimate Member
    Apr 26, 2009
    2,258
    Baltimore, Md
    If you just shim one ring, with a flat shim, the inner ring surfaces with not be parallel.

    You need to shim both front and rear with properly tapered shims.



    Still won’t line up. The front ring needs to be lower, not just shimmed. All shimming is is tilting the rings forward. The back of the hole in the ring will be higher than the front. With shims, the back of the front ring will be higher than the front of the back ring.

    OP, you have a nice set up. Don’t get cheap now. I’m sure egw or the like has a canted base. You are asking for problems shimming them.
     

    rtse4me

    Active Member
    Apr 12, 2013
    298
    Howard County
    OP, you have a nice set up. Don’t get cheap now. I’m sure egw or the like has a canted base. You are asking for problems shimming them.
    DIP does make a 25MOA rail for my Sako Finnfire. I heard the set screws mar up the top of the receiver so I was trying to think of alternatives

    The scope I have currently has 80moa total travel and would like 50+moa of elevation.
     

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    Pinecone

    Ultimate Member
    MDS Supporter
    Feb 4, 2013
    28,175
    Still won’t line up. The front ring needs to be lower, not just shimmed. All shimming is is tilting the rings forward. The back of the hole in the ring will be higher than the front. With shims, the back of the front ring will be higher than the front of the back ring.

    OP, you have a nice set up. Don’t get cheap now. I’m sure egw or the like has a canted base. You are asking for problems shimming them.

    The rear shim would need to be thicker. DUH. :D

    Shimming with flat stock RAISES the ring. Shimming with angled stock, raises and tilts the ring.
     

    nedsurf

    Ultimate Member
    Feb 8, 2013
    2,204
    If you just shim one ring, with a flat shim, the inner ring surfaces with not be parallel.

    You need to shim both front and rear with properly tapered shims.

    Do you think lapping could solve this or would it be too much difference?
     

    atblis

    Ultimate Member
    May 23, 2010
    2,011
    A quick cad drawing and some guesses about ring spacing and size (1" rings, 0.5" wide, 3" spacing center to center), I get that you'd need to shim the rear base up ~0.022", and lapping would need to remove ~0.004" of material. Lapping might be an option because to me that doesn't sound like that much. Another (and possibly better) option is reaming. 1" spiral hand reamer works on horizontal split rings.

    http://pacifictoolandgauge.com/scop...eamer.html?search_query=ring+reamer&results=6

    ETA: Again, I'll pose the question as to what it is you're trying to accomplish. These look like hunting rifles from the pictures. What scopes are you running because some scopes have a very limited amount of adjustment.
    For example:
    1" tube Zeiss Conquests had like 60 MOA of elevation giving you like 30 MOA to work with assuming starting centered
    Viper 6.5-20x50 PA-Dead-Hold BDC (MOA) Dimensions (in inches) has 65 MOA of elevation, so ~33 MOA usable
    Leupold VX-3i 4.5-14x40mm (30mm) Side Focus CDS Options has 113 MOA, so 56.5 MOA usable.
    Sightron SIIISS624X50LRWDP Has 100 MOA, so 50 MOA usable
    Super Sniper 3-15x42 Tactical Rifle Scope has 140 MOA, so 70 MOA usable
    Depending on what your current scope is, a different scope could easily buy you that 25 MOA you're after.
     

    rtse4me

    Active Member
    Apr 12, 2013
    298
    Howard County
    My main objective is to shoot my Sako Finnfire 22lr out to 300 yards so I will need 15 Mils of elevation or about 50 MOA.
    My scope is a Athlon Ares BTR.
    https://athlonoptics.com/product/rifle-scopes-ares-btr-4-5-27x50/
    Just want to practice shooting long range. I have a 6.5 Creedmoor, 6.5 Grendel and 6.5 Swiss and only shoot them once or twice a year since there is no ranges close by.Shooting 200 yards with a Creedmoor gets boring pretty quick.
     

    atblis

    Ultimate Member
    May 23, 2010
    2,011
    You could try the trick of putting a piece of lead shot under the set screw
     
    Last edited:

    ironpony

    Member
    MDS Supporter
    Jun 8, 2013
    7,189
    Davidsonville
    I had a similar problem, both Evolution Gun Works and Vortex told me to shim. EGW also told me this is a known problem with the Vortex Viper PST 6-24 x 50.


    I also got crap from people here for even wanting the capability to adjust properly over 800 yds ... which in my mind is similar to asking why a 30 rnd mag, semi-antis?
    Good Luck OP, call some companies ... they love to help.




    7mm Rem Mag in my case.
     
    Last edited:

    1time

    Ultimate Member
    Apr 26, 2009
    2,258
    Baltimore, Md
    You could try the trick of putting a piece of lead shot under the set screw



    This is what I would do. Use the DIP base. You out a piece of lead shot in the hole so it doesn’t scratch you receiver. It is a very common solution for CZ’s.

    I maintain that shimming 2 piece bases with separate rings will cause more problems than it will solve. If you are great with math and have really good machine skills it could be done. Both shims would have to be at the same angle and the rear shim would have to be the perfect thickness to align with the angle created by the shim.

    On my 22 I use a 20 moa base and adjustable rings. I can adjust from 10 yards to just short of 400 yards. I have plenty of reticle for an accurate dial +hold for 400 yards.
     

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