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1/2 scale AR-15

Discussion in 'Rifle Country' started by MachIVshooter, Oct 6, 2014.

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  1. rcmodel

    rcmodel Member in memoriam

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  2. MachIVshooter

    MachIVshooter Member

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    Thanks, RC. I'll be watching the one on eBay. Unfortunately, Clark was completely out of everything .17 HM2 :(

    Did make more progress over the last 24 hours, though. Attacked the secondary sear. Midway:

    IMG_1154_zps4e133d20.jpg

    And done:

    IMG_1155_zps4fc77114.jpg

    That critter wasn't too bad. Can't say the same for the Hammer, though. That was just as much work as the trigger. I also have not been able to find blueprints for the fire control parts, been having to reverse engineer everything.

    Basic hammer dimensions roughed out:

    IMG_1156_zps15179b31.jpg

    Profiling radii on the rotary table:

    IMG_1157_zps69b9a4c4.jpg

    Cutting the pin detent spring slot with a 1/32" end mill. Did break one. Dime shows just how tiny a 1/32 cutter is:

    IMG_1158_zpsb6aae5ba.jpg

    Done:

    IMG_1159_zps42189f5d.jpg

    Installed:

    IMG_1160_zpsc0bbbb90.jpg

    IMG_1161_zps78409d1a.jpg

    I did bend up a hammer spring, but gonna have to revisit that one; not nearly powerful enough to get the job done.

    Had to play with primary and secondary sear engagements quite a bit before everything worked right, but it's as it should be now.

    Also got the RE housing tapped

    IMG_1163_zps9b05474f.jpg

    We'll see if I have time for the selector tomorrow!
     
  3. jerkface11

    jerkface11 Member

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    Aren't AR15 trigger parts surface hardened? If so do you have the means to do that?
     
  4. MachIVshooter

    MachIVshooter Member

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    For these small parts, yeah. An acetylene torch (or even MAPP gas) can handle such little pieces.

    Having said that, D2 tool steel is quite a lot harder and tougher than the PM or die cast standard 1:1 AR triggers. Untreated, it's still hard stuff, about 250 Brinell when annealed, IIRC.
     
  5. jerkface11

    jerkface11 Member

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    Ok what are you planning on making the bolt out of?
     
  6. Justin

    Justin Moderator Emeritus

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    How are you planning to do the furniture?

    I guess that milling out a stock or grip from a piece of plastic probably isn't that big of a deal, right?
     
  7. Exibar

    Exibar Member

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    This is one of the best threads I've seen in a long time. I saw a 1/4 scale lower someone made when they first setup their CNC. But this 1/2 scale is way cooler and will be functional to boot!

    keeping my eye on ya!

    Mike B
     
  8. MachIVshooter

    MachIVshooter Member

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    Yep. I've got hunks of ABS and Acetyl. It'll be a pain to get the geometry nailed down, but the cutting part is easy! I may very well reprofile a piece of heavy wall 1-1/4" ABS for the hand guard, rather than cut the thing from a block
     
  9. The_Next_Generation

    The_Next_Generation Member

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    I love how this is actually happening and isn't just some "wouldn't it be cool if" kind of thread :D

    KEEP THE PICS COMING. I need more procrastination material...:evil:
     
  10. MachIVshooter

    MachIVshooter Member

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    Selector is done. If I had it to do again, my order of operations would differ, thus preventing the oops which resulted in the lever being off center by about 0.015". I cut the axis first, profiled the lever after. This resulted in having to clamp a round part and make longitudinal cuts a good bit away from the axis. Well, it rotated, and the cutter bit in. Still looks fine from a couple feet away, but you can tell upon close inspection. I originally thought I'd just radius the whole profile for simplicity's sake, but decided to go all the way, cutting the grooves along the entire profile of the lever. That was a pain. Remember, this selector is just .590" long, and the lever .120" wide

    IMG_1165_zpse4854ac5.jpg

    IMG_1164_zpsa37031ae.jpg
     
  11. Dr.Zubrato

    Dr.Zubrato Member

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    this is so cool, I'd love to see this come to fruition!
    Thanks for the continued updates!
     
  12. bannockburn

    bannockburn Member

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    Coolest build thread ever! Looking forward ,like many others following this project, to the finished mini-gun.
     
  13. Jim Watson

    Jim Watson Member

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    You could probably find a takeoff .22LR barrel easier and cheaper than a .17.
    But if you just gotta have that Tactical Bottleneck look...
     
  14. bullzeye8

    bullzeye8 Member

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    This project is really cool. I would really like to see it though if you could get a camera set up and video tape a little of you doing it just so we can see your process that would be awesome.
     
  15. MachIVshooter

    MachIVshooter Member

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    Pretty much :D I'd love to do Eichelberger .12 LR , but for now, .17 M2 will suffice.

    Is there a particular process you're interested in seeing? Because filming the making of an entire part is going to be a very long, very boring video, seeing mostly measuring, moving parts from vise to rotary table and back, squaring up/centering, edge finding, setting DOC, etc.

    Watching someone run manual equipment is not nearly as exciting as watching a high speed CNC zip around and carve out a complex part in minutes. It's more like watching the turning of the CAD file into CAM that happens for hours and hours before the cutting begins.
     
  16. DT Guy

    DT Guy Member

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    People with tools and skills like you must give Pelosi and Bloomberg fits...the ultimate 'Micro Ghost Gun'!

    This is awesome....



    Larry
     
  17. popper

    popper Member

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    Extremely cool real project. There are gas systems other than the Stoner type that are much simpler and work good. Seen too many S-A go full due to disconnecter floating FP problems.
     
  18. WestKentucky

    WestKentucky Member

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    "Oh dear...if they can make these so small then they can make them do all sorts of evil things." Hehe. Sometimes I wonder about our political leaders, and the non-political who throw money around to try to influence popular opinion. Next thing they figure out will be that people might sell things like this or attach those shoulder things that go up.
     
  19. bainter1212

    bainter1212 Member

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    Tag. Cool thread.
     
  20. shotgunjoel

    shotgunjoel Member

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    It's been almost a week, some of us can't handle this kind of suspense.
     
  21. WestKentucky

    WestKentucky Member

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    I was hoping for an update when I clicked the thread...where oh where might this build have progressed to?
     
  22. MachIVshooter

    MachIVshooter Member

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    Family problems have brought many things to a screeching halt. Also, please understand that the progress made in week one was unusually fast due to a lull in the work load; ordinarily, I can't dedicate more than 6 or 8 hours a week to this stuff. If you watch machinist forums, model engine building forums, etc, you'll find that these more complex projects typically see completion over several months, if not years. Lastly, the boring bar I'd ordered was not quite long enough once chucked in the head, so I had to go a different route and buya .465" full length reamer. It showed up today, but I'm not sure when I'll have time to really get back after this.

    I did get the lower sanded almost completely free of tool marks, though. Makes it much easier to see contours in pics:

    b982230e-7dbd-4834-85a6-8325af9533ff_zpsa3558a25.jpg
     
  23. barnbwt

    barnbwt member

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    Months? But I wanna see it NOWWW!!!! :mad:

    :D I kid, but I do think this is why 'build' threads never seem to thrive around here; too many people want instant gratification, even in something as vicarious as following someone else's build. I, at least, am glad there's other members on here who occasionally build stuff from scratch or do original designs :). A nice change from all the monotonous AR "build" threads about identical piece-together jobs (no offense to AR assemblers or their guns, it's just the assembly process isn't that interesting, mechanically :p). Your progress has been blindingly fast; I'd assumed you were retired, or something :D. Heck, my Skorparev project is nearly two years old, only completely designed the last six months or so, and I've only got 5 parts roughed-out! Granted I'm doing everything with handtools, but that's slow even by Khyber Pass standards :eek:

    When you do get a chance to get back on this, promise us one thing; when you go to shape the bolt body, please carve up the breechface to look like a miniature Stoner Sprocket. It'll really sell the 'Mini-15' (come up with something better than 'mini-15' also; I can't do any better at the moment) concept without adding complication in the form of a gas system. A mini gas key would be neat as well, but you'd only see it upon disassembly.

    As small as your bolt tube is gonna be, you may have to scavenge some tungsten endmills or something to get things heavy enough. Even low-pressure 22LR needs a 1/3rd lb or so bolt, and 17 will need a good bit more. Have you run numbers for how heavy a bolt you'll need, and how much bolt volume you likely have to work with? I guess at worst you can always attach a 'piston' rod to the gas key that extends forward under the handguard to gain some weight in an unseen area.

    TCB
     
  24. burrhead

    burrhead Member

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  25. WestKentucky

    WestKentucky Member

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    True, build threads do take a while (even in real life...Wife is tired of my motorcycle build) but something this cool is captivating. MachIV when you get back on this you have to make sure no angry capuchins raid your arsenal and try to take over the world with properly sized weaponry.
     
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