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Thread: Scope drilling jig

  1. #1
    Boolit Buddy Gobeyond's Avatar
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    Scope drilling jig

    Can one of these work for an amateur with a drill press? They have a jig on gunbroker for $147. This might be less than a gunsmith to do a drill and tap. Sportsman’s warehouse wants 35$+ 25$ per hole on hardened metal to install mounting blocks. I don’t want to send my gun to Colorado. 150$ dollar jig ought to keep everything in line as it should be, but maybe it’s just for the innocent.

    How much would a gunsmith charge? Are the jig a good investment? The best way to go is…

  2. #2
    Boolit Master Shopdog's Avatar
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    From an investment perspective;

    I've bought/sold "shop" equipment for 40+ years. #1- do your research. Your best chance for resale will be with well known higher quality items. Buy used-sell used will work out better over the long haul.

    You didn't mention the manufacturer? Assuming Forster..... check new pricing if available. I don't think $150 is out of line...

    You can always use it for a few projects... learning to either make it work for you,or if it doesn't,send it down the rd. At some point in the future brick&mortar gunsmithing is going to be extinct.

    There's drill presses.... and then there's DRILL PRESSES. So to answer whether or not it's going to work hinges largely on the machine. Good luck with your project.

  3. #3
    Boolit Master
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    I have a floor Model Chinese drill press with a Chinese X-Y table bolted to the moveable platform. As long as the Forster jig is level, I have had no trouble drilling and tapping holes for scope blocks and mounts.

    Lacking the jig, I wouldn’t dare do the job on anything but a Bridgeport type milling machine. The X-Y settings keep trying to “drift” a thousandth or three in the course of a job, and even when it is locked down, I have to watch for this. But the bushings on the Forster jig keep everything at top dead center and in line.

    Lucked out and found the jig, missing clamps and bushings, for $25 at a gun show. Ordered the clamps from Forster, made the bushings myself, and have done a half-dozen barrels since. A lot of these barrels already have off-center threaded holes that I have to fill before drilling around and covering with the properly installed scope blocks. As far as I’m concerned, the Forster paid for itself with the first tapped hole I made.

  4. #4
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    Larry Gibson's Avatar
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    I have been drilling and tapping receivers for bases since '70 using a floor drill press w/mill table to hold the Forster jig. There is a reason Gunsmiths charge $35 + $25 per hole. It has to do with time, precision and the knowhow. The time to log the firearm in as per fed regs, set up time including disassembly and assembly of the firearm. It includes the quality and precision of the equipment to do the job correctly. It includes the knowhow to do the forementioned along with where to drill the holes in the receiver.

    There's lot's of "bubba'd" d&t'd actions out there.........
    Larry Gibson

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  5. #5
    Boolit Master pertnear's Avatar
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    I used my table-top drill press to D&T my Martini barrel for a TC-Contender base. I rented the jig from 4D. Unless you intend to do a bunch, rent is my recommendation. Be sure you have the right bottom taps available.
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  6. #6
    Boolit Man
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    All good observations above. I'll add that if you are drilling Mausers or other case hardened receivers, read up on the subject before you turn on the drill.

  7. #7
    Boolit Grand Master

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    Drilling and tapping a receiver isnt always the easiest to do. you can run into hardened receivers that require annealing to just get thru the case. Small drills and taps to work with. I would recommend before doing an action you practice on a piece of scrap. even a piece of round stock the correct dia and you can get 4-6 runs around it. The XY table is a big help but there is a lot of differences in them as well. You want to learn your machines so there are no surprises. Drilling holes on a radius is harder than flat. A good center drill to start then drill to depth a solid stop is needed here. then a light chamfer and tap to depth. Practicing a few times will get the skills started and give an idea of whats going on. Its better to break a drill or tap in the cold rolled steel practice than a receiver.

  8. #8
    Boolit Buddy
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    Quote Originally Posted by Gobeyond View Post
    Can one of these work for an amateur with a drill press? They have a jig on gunbroker for $147. This might be less than a gunsmith to do a drill and tap. Sportsman’s warehouse wants 35$+ 25$ per hole on hardened metal to install mounting blocks. I don’t want to send my gun to Colorado. 150$ dollar jig ought to keep everything in line as it should be, but maybe it’s just for the innocent.

    How much would a gunsmith charge? Are the jig a good investment? The best way to go is…
    Buy it. Even though I have trouble storing what I have, it would not bother me one bit to have the problem of where to store a Forster jig. My buddy has one and they are handy for more than just mounting scope bases.

  9. #9
    Boolit Master Rapier's Avatar
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    If it is a Forster, the new prices are close to $500 today. The hardened drill and tap guide tubes come extra. Bought mine near 30 years ago from a shop that was closing for about $150 figured it was a deal. Hard to hurt them, unless you do something real dumb.

    If you ever see a line of holes drilled off the axis of the bore, you get the reason for the Forster.
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  10. #10
    Boolit Master
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    I've drilled and tapped over a dozen Mauser receivers. Here's some of the things I've seen. First, if the barrel is removed there's no reason for blind holes and bottoming taps. Through holes can be drilled and tapped. Make extra sure that you do not drill into the face of the upper bolt lug recess on the receiver. (I've seen this on a couple of Bubba'd receivers) Use either a carbide drill, or better yet, a carbide tipped drill, and the case hardening will not be a problem (no need to spot anneal). Specialty "hard metal" taps work very well on case hardened and heat treated steels, but I have yet to find them in the size/pitch commonly used for scope mounts. When using high speed steel taps you need to work carefully and break the chip often by backing the tap out slightly while cutting. The danger of breaking a tap off is real, so a steady hand and repeated small cuts are required. The place where there's the greatest chance for a broken tap, and where the cut needs to be made most carefilly, is the scope hole at the front of the receiver ring. This is because the hole that is being tapped passes through the receiver threads, which are case hardened and are an angled surface to the axis of the scope mount hole.

    When I'm mounting a Redfield/Leupold style standard base to a receiver I use the scope base to position the mounting holes. The top of the scope base must be parallel to the flat surface on the bottom of the receiver. The position of the base must be such that the mounting holes will not interfere with the lug abutment inside the receiver. With the base in this position I clamp it in place and then use transfer punches to index the positions to drill. I have a very old, but very precise Walker-Turner floor mount drill press with an adjustable X&Y axis vise, plus a fixture to hold Mauser receivers when using a vise on a mill or drill.

    Two piece mounting blocks are a little more tricky. For those I take the measurements that I want, then machine my own drilling jig from a small piece of bar stock. On some receivers, like P14 Enfields where I machine on the rear bridge, or on custom made receivers where there are no factory scope mounts that match those dimensions, I just machine my own scope mount. This is not necessarily beyond the capabilities of folks that don't own a milling machine because picatinny rail can be purchased in several lengths, and much can be accomplished with a drill press and some files.

  11. #11
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    I did alot of research, and counciled with a retired machinist who'd done dozens of them in the 50s
    before I drilled & tapped the receiver on a unissued 03A3. (It came out perfect)
    At the time, I paid very close to the cost of having it done as I spent on the right drills & taps, that I never used again.

    Not being nearly as young and stupid as I used to be, now days, I'd just have sent it out,
    and paid the price for someone who had done them a few dozen times more than I ever will.

    In your research, don't forget to ask your self how all the big savings will be computed if you mess up the receiver.

    I'm reminded of myself when a life long friend and mechanic was overhauling the lower unit steering box on a old car I had.
    I kept asking questions so I could do the next one by myself.
    He finally told me, "If you have to ask questions like that, you shouldn't be doing this".
    In school: We learn lessons, and are given tests.
    In life: We are given tests, and learn lessons.


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  12. #12
    Boolit Buddy Gobeyond's Avatar
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    These stories are just sending me right to the gunsmith. I was a sheet metal mechanic and precision is largely beyond me. Even when working with 1/32 tolerances. I can make a jig but not with .001-.003 tolerance. My gunsmith has a mill I will leave it to him to do. Thank you for clarifying.

  13. #13
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    Winger Ed.'s Avatar
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    That's what I'd do.
    Whatever your home drill press can do---- the gunsmith's ga-zillon dollar mill can do better.
    In school: We learn lessons, and are given tests.
    In life: We are given tests, and learn lessons.


    OK People. Enough of this idle chit-chat.
    This ain't your Grandma's sewing circle.
    EVERYONE!
    Back to your oars. The Captain wants to waterski.

  14. #14
    Boolit Buddy
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    I haven’t wrecked anything, but my buddy accidentally drilled a hole through the locking lugs on one of my receivers once. He offered to replace it, but he has done so much for me over the years that I told him not to worry about it. He answered the phone in the middle of doing the job.

    It’s a Remington 580 that had been threaded for the barrel shank and I intended to use a CF converted bolt in it. No big deal, they are a dime a dozen. I have it sitting here and it is fine to use to build up a real nice 22 LR on.

  15. #15
    Boolit Master
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    I had a shirt tail relative drill a Mauser action for me many moons ago. I had spent more than I should have on the optic. Shot #5 through the rifle sent a mount screw through the scope I had invested in. After being the toddler that burnt his fingers - I pay whatever my smith charges with a smile.

    Sent from my Pixel 5 using Tapatalk

  16. #16
    Boolit Master
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    I have seen a lot of the Bubbasmiffed Mauser actions that Larry mentioned over the years. Don't be Bubba.
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  17. #17
    Boolit Master

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    It has always been fun to repair holes that were drilled in the wrong place. Mausers are case hardened ( no problem) Springfields are hard all the way. Please don't drill holes on pre war model 70 Winchesters.

  18. #18
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    M-Tecs's Avatar
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    Quote Originally Posted by cwtebay View Post
    I had a shirt tail relative drill a Mauser action for me many moons ago. I had spent more than I should have on the optic. Shot #5 through the rifle sent a mount screw through the scope I had invested in.
    Which screw and where did the pressure come from?
    2nd Amendment of the U.S. Constitution. - "A well regulated Militia, being necessary to the security of a free State, the right of the people to keep and bear Arms, shall not be infringed."

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  19. #19
    Boolit Master
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    Quote Originally Posted by M-Tecs View Post
    Which screw and where did the pressure come from?
    It was the front center base screw. All I could figure is that he had drilled into the the chamber?

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  20. #20
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    Quote Originally Posted by John Taylor View Post
    It has always been fun to repair holes that were drilled in the wrong place. Mausers are case hardened ( no problem) Springfields are hard all the way. Please don't drill holes on pre war model 70 Winchesters.
    I rebarreled a buddy's 98 a while back. He had it originally built by a well know west coast big name gunsmith. He had the holes in the proper location, but the original smith apparently could not get it to tap so he drilled the holes to the #6 OD and epoxied them in. That held for around fifty years. When the screws came out he took it to the local gunsmith. The local gunsmith gave up after toasting 4 or 5 8-40 taps even after spot annealing. I live about 500 miles away. My buddy contacted me to fix the holes and to put a Krieger barrel on it. A carbide thread mill had no problems cutting larger threads. Not sure why the case on that one was so deep?
    2nd Amendment of the U.S. Constitution. - "A well regulated Militia, being necessary to the security of a free State, the right of the people to keep and bear Arms, shall not be infringed."

    "Before you argue with someone, ask yourself, is that person even mentally mature enough to grasp the concept of different perspectives? Because if not, there’s absolutely no point."
    – Amber Veal

    "The Highest form of ignorance is when your reject something you don't know anything about".
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