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Mauser 98 weaver scope base help

Discussion in 'Gunsmithing and Repairs' started by mookiie, Mar 1, 2013.

  1. mookiie

    mookiie Well-Known Member

    I have a mauser M48A action that has holes drilled for a weaver style scope base. The rear holes (closest to the shooters face) do not match the standard Weaver base # 45. The holes are too far apart to fit this base. The distance between the center of the two holes is about 13/32, actually looks to be 3/8. I am trying to identify a weaver base that will fit these pre-drilled holes. Can anyone help me? Thanks!

    I have been looking on-line but I would probably order 4 different bases and have none of them match with my luck! :banghead:
    Last edited: Mar 1, 2013
  2. Kp321

    Kp321 Well-Known Member

    I fear that you won't find a base that will work. The Weaver 45 will barely fit on the rear ring. I am not aware of another base that has a greater hole spacing that will fit the available space.
  3. mookiie

    mookiie Well-Known Member

    I actually need a base that has the holes closer together than the weaver 45.
  4. MR

    MR Member

    I think it may be drilled for the Leupold 98 Mauser 2 piece base that fits over the charging clip hump, if the holes are that close together. my best guess with out seeing it.
  5. mookiie

    mookiie Well-Known Member

    Here it is. The front two holes fit the weaver 46 perfectly. The back two (on the left in pic) are to close together for the 45:

    There are also two holes on the right side of the rear of the receiver which i can only guess was for a lyman peep sight.
  6. mookiie

    mookiie Well-Known Member

    Anybody have a large stock of weaver bases they could measure the holes on to see if they are 3/8 apart? Please need some help on this one. More problems than I anticipated for this build!
  7. Jim K

    Jim K Well-Known Member

    If you can't find an exact fit, you can buy a long Weaver base with the holes widely spaced, drill a new hole in the base as necessary and then cut off the excess.

  8. mookiie

    mookiie Well-Known Member

    Jim- awesome idea! This can solve it for me! Thank you sir!
  9. Reloadron

    Reloadron Well-Known Member

    This is a guess but a base with 3/8" (.375") hole spacing is Warne Maxima 2-Piece Steel Weaver-Style Scope Base Remington 799, Interarms Mini Mark X, Charles Daly Mini Mauser Gloss. Here are the specifications:

    Package contains two bases. First is .960 long with .625 hole spacing (center to center), second is .830 long with .375 hole spacing (center to center). Product photo shows longer base where slot is offset toward one screw hole. Shorter base has slot centered between the two screw holes.

    The rear Weaver equivalent would be a Weaver Top-Mount #23 Weaver-Style Rear Scope Base Remington 799, Interarms Mini Mark X, Charles Daly Mini Mauser Gloss. So my guess would be a Weaver #23 base for .375" center to center hole spacing.

    I like Jim's suggestion as I have done that also.

  10. BBBBill

    BBBBill Well-Known Member

    I'm with MR. I think it is a drilled for a Leupold or similar.
  11. mookiie

    mookiie Well-Known Member

    well the hole spacing on the weaver 23 mount, but the base is machined for a smaller action than the large ring m48. Not sure what to do now. The only other thing I can think to do is drill and tap a new hole for the original base. do you think it would weaken the rear of the action to much to put a third hoke on the top?
  12. BBBBill

    BBBBill Well-Known Member

    Probably won't hurt, but I would not do it without exhausting all other possibilities. As I noted, it looks like a Leupold hole spacing. Measure carefully and check with Brownells tech support. If you stuck on Weaver, drill another hole in the sight base and save that receiver from further abuse.
  13. mookiie

    mookiie Well-Known Member

    Well I called brownells and they said the hole spacing is .325 and the actual holes in the receiver seem to be about .400 apart at center so I am leaning towards cutting a new hole on one of the weaver mounts I have.
  14. Clark

    Clark Well-Known Member

    I am a walking Mauser Junk yard, starting in 1965, but really got going in 2000.

    I buy Mauser that are screwed up, just for parts.
    The usual screw up is the scope mounts.
    I waller over the hole, the countersink, and the concave radius on the bottom. I shim and glass bed so that the mounts are co planar and parallel with the bore. [ or pointing 20moa downward if we dress up and play sniper]. Notice the boring head marks on the bottom, ala Steve Ackerman.

    Attached Files:

  15. mookiie

    mookiie Well-Known Member

    Clark can you elaborate? I am not sure what you are suggesting.
  16. Clark

    Clark Well-Known Member

    When holes in the receiver don't match holes in standard mounts [base] or are off center, one can:
    1) Drill and tap more holes [Swiss Cheese solution]
    2) Weld over the holes and start over [Nuke option]
    3) Make a custom mount [ all day long option]
    4) Screw something down and lapp the rings [wreck the rings]
    5) Modify the mount [ mod the cheapest part]
    6) Don't get involved

    I have been going for option 5)

    To modify the mounts [Brownells calls them Weaver bases] I have modified a pair of V blocks.
    Those hold the mounts by the edges.
    I move over [make oblong] the hole with an end mill the same size as the hole.
    I move over the countersink with an end mill the same size as the countersink.

    I change the bottom radius height, radius size, or centering with an end mill [if there is one the right size] or boring head.

    The alignment procedure starts by centering a reticle in a scope body. I used to put a scope in half rings and rotate, and then adjust the elevation and windage until the center of the cross hairs stayed on one spot on the target. Now I press the objective against a mirror and adjust until the two cross hair images over lap.
    Then the screws to the mounts are put in loose. The scope is shimmed [with narrow stacks of tape] until the centered scope bore sights. Then wet epoxy is put between the mount and receiver. The scope is checked for bore sight again. When the epoxy hardens, the screws are removed, threads are cleaned, and the screws are tightened with loctite.
    The scope should then be sighted in when centered and no ring lapping needed or desired.


    Attached Files:

    Last edited: Mar 8, 2013
  17. BBBBill

    BBBBill Well-Known Member

    Leupold sells "gunmaker" bases for just that purpose. Drill yer own holes. Machine yer own radius. Clark's method of slotting the screw hole and countersink is going to be your fastest, safest, cheapest solution if you cannot find a base with the correct c to c spacing, bottom radius, and height. Beats the heck out of putting more holes in the receiver.
  18. mookiie

    mookiie Well-Known Member

    My problem is I do not have access to milling machines to do the work for something like that. If I could cut the radius I would be set because mini Mauser weaver 23 is perfect for the hole spacing, but the radius cut is not shallow enough to match the large ring radius. Right now I am leaning towards either cutting a third hole, or using a base and trying to drill a third hole in the mount fixture. Mostly because those are the only two methods I have the tools to do correctly. Thanks for all the details Clark!
  19. BBBBill

    BBBBill Well-Known Member

    Got a drill press and a way to securely clamp the base while you drill it? I would not normally suggest using a drill press, but a decent job can be done on a simple hole and counterbore. Or why not take it to a machine shop and have them modify the base? Heck, I could probably do it with a rat tailed file and a hand drill in a pinch. Still, the hole spacing is only half the battle. You have to ensure that the base height is correct for vertical ring alignment. Just grabbing any old Weaver base and poking holes in it ain't gonna get you there. Even the ones made for that action must be checked due to the variations in the actions.

    And I'm curious how you are measuring. You first say "The distance between the center of the two holes is about 13/32, actually looks to be 3/8", then "about .400" apart." Do you have dial calipers, are you measuring between the screws, and adding one diameter? I do not wish to offend, but the whole thing is beginning to sound like you are over reaching your level of understanding, skill, and equipment.
  20. mookiie

    mookiie Well-Known Member

    BBBBill - I think you are right about me being out of my league on this task, but I think I can find a solution. So each hole is .14 in the distance between the outside edges of the holes is .530 in. The distance between the inside of the two hole edges is .250. That would mean the distance between the center of the two holes would be .390 in.

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