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Need advice: custom Picatinny or Weaver rail base

Discussion in 'Shooting Gear and Storage' started by Odd Job, Dec 29, 2012.

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  1. Odd Job
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    Odd Job Member

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    Although this is for a crossbow, the problem is going to be solved by good old fashioned firearms-related ingenuity :)

    I have a Cheetah crossbow which I want to put a Picatinny or Weaver rail on (doesn't matter which). This is where it will go (note this is polymer and I can't make any alterations to it):

    RailBasedimensions_zps0ca20186.jpg

    My current thinking is to make this in two pieces: a custom "base" onto which I can secure a rail with a flat back.

    1) The base of the rail must be at least 8mm/0.31" high
    2) The base of the rail must be at least 115mm/4.52" long
    3) The base of the rail must be no wider than 14mm/0.55"

    The base will have to be drilled to accept the two pins which are 3.47mm in diameter (0.136")

    I'll have to get the base drilled and tapped to match the holes in the rail.

    I can also remove that knurled nut in the middle and make use of that hole as a further means to secure the base to the crossbow. That is a 4.85mm machine screw (0.191").

    How would you do it? Is there anything out there which already has a base that could fit?

    Advice much appreciated.
     
  2. Haxby

    Haxby Member

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    Google
    BKL-456 14mm
    That might be what you want, or it might be a starting point.
     
  3. Odd Job
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    Odd Job Member

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    It is too wide, the 14mm is the "inside" dovetail width and I need the overall width 14mm max. I am looking for a one piece base also...
     
  4. rcmodel

    rcmodel Member in memoriam

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  5. Odd Job
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    Odd Job Member

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    That looks like a plan, RC, thanks!

    Look again, I have the measurements in mm and inches hehe
     
  6. Odd Job
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    Odd Job Member

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    Update: this got solved with the help of a friend at the local rifle club. I got one of these 12" blank Ergo rails from Midway UK:

    http://tinyurl.com/d93koqg

    My friend was able to turn that into two of these:

    IMG_2138_zpsc6e7961b.jpg

    Here is the machined and drilled rail next to the mount assembly:

    IMG_2139_zps7be7bcac.jpg

    Here it is, a nice fit:

    IMG_2140_zps64919585.jpg

    IMG_2141_zps6181c209.jpg

    IMG_2148_zps5a58e451.jpg

    IMG_2149_zps2ce1521a.jpg

    I'm very happy with that. The second rail (not shown) is even better because the back end has been ramped to match the mount assembly angle.

    That rail will go on the other crossbow, possibly with a reflex dot sight.
     
  7. rcmodel

    rcmodel Member in memoriam

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    Well, that turned out nice!!

    Good work!

    rc
     
  8. Odd Job
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    Odd Job Member

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    The guy is very good, the rail looks like it was made for the crossbow!
    My next job will be to get some black polyethylene blocks fashioned to fill the hole where the knurled nut used to sit (no longer needed as the rail will not tilt).
     
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