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Thread: bottom mag-fed automag

  1. #1

    bottom mag-fed automag

    First off, I'm not assuming I'm the first one to do this, but I haven't found anyone else who has. That's why I'm posting this build thread.
    Maybe one of you guys will even beat me to the finished product cause I couldn't get to my machinist today so it will be next week before I can get this thing knocked out.

    So here's the build sketch:
    a DYE DAM magwell sits really well on an RTP rail and has enough meat to be held on via the 6 holes already there.
    I'm turning the magwell backward because that more naturally lines the mag feed with the breech.
    I'm going to use a direct feed body for the first trial, but will do it with a centerfeed body if it works well.
    Fabricate a PIM to put over the twistlock hole in the body and drill the rail for this new PIM. The front screw will now not only hold the body and rail together, but will hold the barrel in place.
    This means you need to drill a small hole just in front of the breech on your barrel. It will not twist lock, but will be held in place by the pressure of the screw. With the o-rings on the barrel, it doesn't have to be screwed in super tight, just enough to keep the barrel from moving around.
    Attach the rail to the body and drill the feed hole through both. On the center feed body, I'll just go straight down through the original feedneck.

    drill the mounting holes in the magwell. Again, the original 6 holes in the rail will hold it, but I'm adding a bolt through the foregrip bracket to give it that extra strength.
    the magwell needs a little material removed to allow free movement of the sear.
    I'm going to use a cocker slider frame and fabricate a cocker actuating arm to screw into the sear receiver. I'll bend the arm around the frame so it lines up with the sear. This will give me direct actuation of the sear.
    I'm going to mount the frame to the marker via the field-strip screw hole. This means that screw both holds the valve in place and holds the frame in place.
    Since this leaves the butt end of the frame hanging off the back of the rail, I'm going to use some AL pipe, cut it to length to bump against the back of the valve, and screw the frame to the pipe. I have a sight rail I'm going to put over it to give some continuity to the rear of the marker.
    With the AL pipe at the back, I should still be able to adjust the velocity without taking anything apart.

    Here's a mock up done to make sure everything will fit. That is not the slider frame, or the body I'm going to use, but the rest is ready.



    It really is amazing how well that magwell fits on there.

    I should note that since the DYE mag is technically backwards on the marker, it will not be able to shoot first strike rounds. I have Luke's EP blocks and have looked at a ton of different setups, but this way is the easiest that I could find. I'll get it up as soon as I can.

    If someone else wants to get a jump on this, I did order a second magwell from DYE. It was $50 + shipping. I could get it out tomorrow or Saturday.
    Last edited by bowcycle; 10-30-2014 at 10:16 PM.

  2. #2
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    there is a very well known machinist in CA, Sandiego, has made an amazing bottom fed marker, based off the mag platform. pretty amazing,
    and all done with knee mill.

    I would find out who that is and pick his Hawaiian brain.

    he is a busy man im guessing so don't feel bad when he doesn't respond fast like
    My sydarm weighs less than yours!!!

  3. #3
    I've heard of a couple of people who attempted it, but cannot find pics to save my life.
    If you know of some pics, please post them up. I think my version is something anyone can try. So the more encouragement to go for it, the better.

  4. #4
    I finally got to work on this a bit yesterday.

    I'm confident enough it will work that I went straight for the center-feed body, but used one that had already been chopped pretty low.
    I clamped the body to the rail and drilled straight through both with a small bit, then took them apart to drill each with a 3/4" bit. I used the 3/4" bit to center everything in the press before switching out to the smaller bit.



    With very little cleanup, everything aligns nicely.




    You'll notice that I went ahead and had the PIM seat machined around the twist-lock hole. My machinist can't weld stainless right now, but as soon as I find someone to fabricate a PIM over the twist-lock hole on the body, I will be really close to finished.

    then it was time to line up the magazine, drill it, and mount it.



    I think it lines up really nicely.





    Initial feed tests have been spectacular. I loaded the magazine, put a swab down the barrel and left the valve off the back, then just moved the swab back and forth to see if the balls would feed. It went great! I'm calling the feed part of this mod a success. Now we'll see if I can get a frame on it and get it to fire.
    Last edited by bowcycle; 11-05-2014 at 01:14 PM.

  5. #5
    This is just a mockup, but I'm pretty sure I just solved my sear activation problem with spare parts and without a ton of modding.


  6. #6
    Must admit i thought more people would chime in on this build. Am i commiting sacrelige or is everyone just waiting to see if i can pull it off?

  7. #7
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    "carter machine" if he has time talk to him.
    if he cant talk about the project, understand.

    what he has made, or is making is, in my opinion amazing.

    if all falls through hit me up.

    and remember he does all his stuff on a manual mill. and lathe.

  8. #8
    What I'm hoping to accomplish here is something anyone with a drill press and access to a welder can accomplish.
    I have a local machinist who has done a lot of great stuff for me and is not expensive. But I know not everyone has that. So I'm hoping to keep this build simple to the point that anyone could do it for themselves.

  9. #9
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    Quote Originally Posted by bowcycle View Post
    What I'm hoping to accomplish here is something anyone with a drill press and access to a welder can accomplish.
    I have a local machinist who has done a lot of great stuff for me and is not expensive. But I know not everyone has that. So I'm hoping to keep this build simple to the point that anyone could do it for themselves.
    I have a printed bottem fed mag that works printed.
    just need to fine tune structure.

    carter, has made a setup that is amazing.

    use your outlets and abilities as they come.

    this is awesome to see.

  10. #10
    some updates:

    the only modification necessary to the DAM magwell is the 6 holes in the sides and a slight shave in the center back to allow the sear arm to move freely.




    It naturally sits perfectly on the foregrip mount of the RTP. I'm going to put a bolt through the front of the magwell and foregrip mount, but I doubt it's really necessary. Everything is kind of naturally snug.




    Finally, I think an old Lapco t-stock just saved me some fabrication. It's not going to be pretty, but it is quite functional and will bolt to the RTP rail in 2 places so will be plenty sturdy.




    Obviously that drop isn't going to work, but I already have it switched for something that will both look nice and be quite functional.

  11. #11
    I went to a local welder and $20 got a stainless 10/32 nut tig welded onto the body. if you guys do this, tell your welder to turn the machine WAY down. You want them to go slow and leave a lot of the nut in place. This guy tried to go too quickly the first time and completely ate away the nut.

    I used a bevel-head hex bolt up through the body to center the nut over the T/L hole. I cinched the nut down really well, then had the welder hit it. Once that was finished, I just hit the nut with a grinding bit on the dremel to round it off.





    Because the T/L hole is much larger than a 10/32 screw, I bought an aluminum spacer, opened the T/L hole to 5/16 so the spacer would fit and then bolted the body in place.





    The body lines up perfectly and the valve will cycle on the marker!


  12. #12
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    Do you think this would be possible with a am rail?

  13. #13
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    Quote Originally Posted by yellowmitten View Post
    Do you think this would be possible with a am rail?
    or would you be willing to sell the rail, body and loader?

  14. #14
    Quote Originally Posted by yellowmitten View Post
    Do you think this would be possible with a am rail?
    The am/mm rails don't have enough meat to handle having 3/4" drilled out of the middle of them. Plus, it's nice that the RTP and tac-1 rails already have screw holes that allow for mouting the magwell.

  15. #15
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    Last edited by yellowmitten; 11-19-2014 at 05:11 PM.

  16. #16
    I've been thinking about a magazine fed mag but I think I would like mine to be a side feed with more of the sten/sterling look. can't wait to see this one work.

  17. #17
    Quote Originally Posted by yellowmitten View Post
    I saw that back in 2012. Really wish that thread hadn't died over 2 years ago. Would have been cool to see where that could have gone.

  18. #18
    Quote Originally Posted by vintage View Post
    I've been thinking about a magazine fed mag but I think I would like mine to be a side feed with more of the sten/sterling look. can't wait to see this one work.
    There are a few members here who have done top and side-fed mags. On those, you don't have to move the frame or drill the rail. So it's really just a matter of drilling the side of the body, milling the barrel to feed horizontal, and attaching the magwell to the body. I know at least one guy 3D printed a magwell with a "cuff" that slid over the body. If it were me, I'd probably just dremel a thin stretch of material out of the rail in 2 places so I could hose clamp the magwell straight onto the body.

    If you have access to a machinist, another option would be to make 2 small aluminum blocks that the magwell can bolt onto and then braze those onto the body in the right place. It would look cleaner and be a lot more stable than the hose clamps. The blocks would be flat on 5 sides and radiused to the body on the other side. Probably an easy build.

    All of this gets even easier with a Doc's cocker adapter. I think that will probably be how I finish this build, but we'll get it knocked out this way first.

  19. #19
    Had the work done on the frame last night. It serves its purpose really well, but I need to shave some meant from under the rail so the stock can fit in there and still let my trigger fix sit under the frame screw. there might be an easier way to do this, but I haven't found it. Feel free to offer up advice.






    and just a note, the way the actuator sits on the trigger plate still allows you to use an allen wrench to tighten the frame screw.

  20. #20
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    oh oh,


    when you are done, make a dual mag like this.

  21. #21
    KNM, your link isn't showing.

  22. #22
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    Quote Originally Posted by bowcycle View Post
    KNM, your link isn't showing.
    what # post?

  23. #23
    Quote Originally Posted by knownothingmags View Post
    what # post?
    I thought you were going to link something with the word "this" in post #20.

    I see now it doesn't have to be interpreted that way. What do you mean by "dual mag"?

  24. #24
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    Quote Originally Posted by bowcycle View Post
    I thought you were going to link something with the word "this" in post #20.

    I see now it doesn't have to be interpreted that way. What do you mean by "dual mag"?
    oh I meant make a dual mag setup with the design you are doing now. bottom feed and such.

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