Shimming a Scope !!

Discussion in 'Gunsmithing' started by SWO1, Oct 12, 2012.

  1. SWO1

    SWO1 Well-Known Member Lifetime Supporting

    2,866
    41
    Spent all yesterday afternoon mounting and sighting in the neighbors Rem. 770 .308. Replaced the Package scope that went out in 4 shots with a Centerpoint 4X16. They come with their own rings. Bore sighting and shots from 25 yds maxed out the elevation and left it at 14" low. This will equate to around 10" at 100 yards.

    So obvious solution is to shim the scope. 2 possible fixes are:

    Shim the base (rear)
    Shim the ring (rear)

    Personnaly I perfer to shim the ring first. The scope on my Rem 700 is shimmed on the rear ring and has been for about 7 years and still holds sub .5" groups with hunting loads.

    I use aluminum cans, take your pick, Beer (any brand will do), Soda, I used Mountain Dew as it was the first one I picked out of the recycle barrel. I cut the top and bottom off with avaition shears using the side metal. I washed the metal and sprayed it down with brake cleaner and wiped good. I then cut strips to match the ring width and length to go UNDER THE SCOPE, BUT NOT ON THE SIDES. For this application I used 2 strips.

    On remounting the scope, bore sighting and re-firing at the 25 HAD PLENTY OF ELEVATION. Moved back to the 75 and had to COME DOWN ABOUT 32 CLICKS to get it centered. Worked great.....again.

    Note: If your prefer to shim the base, which I have, May I suggest to use a piece of Old Measuring Tape. The contour is just about right to fit the curvature of the barrel, and even is the mounting surface is flat it will flatten out fine. Just drill holes. Only problem with base shims is SOMETIMES the screws with the origional base will not be long enough and you will have to obtain new ones.
     
    Last edited: Oct 12, 2012
  2. Bucky

    Bucky Well-Known Member

    727
    0
    SWO1
    I tried coke canshims on my .444, but did not like the way in which it was clapming down
    In the end I used Grey Tape, just 2 layers to start with, but I had to back it off
    That was 9 or 10 years back, and it still works fine.
     

  3. greyhawk50

    greyhawk50 Well-Known Member

    1,970
    0
    I have had a couple that needed shimmed. I always shimmed the rings with black electrical tape. Got the idea from a set of Burris Rings that came with tape shims in the rings.
    I've never used them but there are shim kits available for the bases. http://www.brownells.com/.aspx/pid=914/Product/SCOPE-SHIM-KIT
    There are several shim kits for the base on-line. Burris, Brownells, Hart.
    I wish you success in getting it sighted in.
     
  4. SWO1

    SWO1 Well-Known Member Lifetime Supporting

    2,866
    41
    Thanks Bucky, and Greyhawk for the comments on tape. There is always a solution to every problem (more than one) without spending time and money. thats what I like about this forum, experienced people that give sound advice THAT WORKS. Thanks again guys........:cool:

    Oh, and the reason I dont use beer cans is.....I only drink mine in BOTTLES, the glass is to thick.......:D
     
  5. Bucky

    Bucky Well-Known Member

    727
    0
    Love it
    Hehehe !
     
  6. Spoon

    Spoon Well-Known Member

    560
    0

    Sounds like you either need a bartender with a better supply of beer bottles or a machinist friend with a good supply of shim stock along with a computer to run the logarithms to get the max flexibility out of your shimming jobs. Had to take a poke. I've never encountered such troubles, but I'm not a LR bench poker that may need some extra measures built into a shooting system! I did install mounts one time that bass ackerds that through me for a loop...but luckily noticed and corrected before cinching the mounts down tight.

    I wonder how many MOA those 2000yd plus kills required with the .338s & .50s took? Probably easier to dope it through the FC system on a mobile 155 than to figure that in a man's head.
     
  7. enbarnes

    enbarnes New Member

    3
    0
    Shimming a Scope

    I use used glucose test strips (they are metal). I'm a bit leery of using anything that is non-metal because it will compress and creep ver time.
     
  8. Hyphenated

    Hyphenated Well-Known Member

    854
    0
    I use Red Bull or Monster cans....my rifles shoot 200fps faster when I'm done. :D :D
     
  9. SWO1

    SWO1 Well-Known Member Lifetime Supporting

    2,866
    41
    Two more scope projects going. Now have a 32X target scope for the 7XVH .223. Will replace the 24X. The 24X I will put on the old Marlin Model 80 that has mis-aligned base holes. I also obtained a set of Millet Adjustable rings to correct the alignment problem on the .22. Deer season is down for about 10 days until Alternative Method in the middle of the month. So have some time to kill at the work bench.
     
  10. Hyphenated

    Hyphenated Well-Known Member

    854
    0
    Wow...a 32 power scope. Are you shooting critters with that or reading the WSJ at a 100yds. :D :rolleyes: I have learned I can't steady high power scopes in the field. Once the magnification hits 12x I need a bench and sand bags. More power to you SWO1. Pun intended.
     
  11. SWO1

    SWO1 Well-Known Member Lifetime Supporting

    2,866
    41
    Its a variable...really wanted a fixed but got this one for $70 new at the gun show yesterday, its a Simmons like my 24X. Just poken holes in paper, but like you if hunting usually dial em down to about 4-6X. And I do shoot off a front rest and rear bag on the bench with the 24X and will also with this one.

    NOBODY can hold Rock Solid Steady, and a scope just magnafies the wobble, even off a rest to some degree....the higher power you go the more wobble you see. I took it down to the bench and could see a Lady-Bug on the Traget Frame at 100 yds, spots and all...............:cool:
     
  12. dugammo

    dugammo Member

    10
    0
    Hello! Just a quick question! Maybe I'm slow which has happened inthe past, but wouldn't you shim the front ring to raise the scope, if your elevation is maxed out? My 30-30 is ten inches low at 50 yds. It would seem to me if I shimmed the rear ring I would drop the nose of the scope more! Maybe I'm looking at this backwards! Thanks
     
  13. Plumber

    Plumber Well-Known Member

    111
    0
    If you're shooting low, you want to raise the rear sight. Always move the rear sight in the direction you want the point of impact to move.
     
  14. Plumber

    Plumber Well-Known Member

    111
    0
    dugammo,
    Think of it like this. Your gun shoots 10" low, so you need to point the scope at the bullet holes. The only way to do this is raise the rear of the scope.
     
  15. dugammo

    dugammo Member

    10
    0
    Thanks! I guess I was thinking backwards. By raising the back of the scope, will that give me back my adjustability?
     
  16. Plumber

    Plumber Well-Known Member

    111
    0
    Yes, but there is a formula for the amount to raise the rear of the scope.
    Will you be shimming the scope or the scope mount?
     
  17. dugammo

    dugammo Member

    10
    0
    I think agree with what you stated earlier. I'll do the scope. Thanks for your info. I'm making one of those cowboy assault riles, 336Y. Looks pretty cool. I can use a ghost ring, red dot, and a standard scope.
     
  18. Spoon

    Spoon Well-Known Member

    560
    0
    Thanks gents. Ran across this guidance and put it to good use on a Benjamin Nitro that I ran out of adjustment on. 2 pcs of Dr Pepper can got it to where it needed to be. - Spoon