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Thread: [Tutorial, kinda] Adding 1 more round to your Keg12 AOW

  1. #1
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    [Tutorial, kinda] Adding 1 more round to your Keg12 AOW

    This is a simple project that I decided to do in a week's time. There are details to be finished but maybe this blueprint will help someone out there even if I don't bother to update this thread.

    A factory Keg12 shorty with a 7" barrel holds 2+1

    If you're okay with using standard 2 3/4 shells you can make it 3+1 and still look like it came from the factory.

    As delivered, I keep it loaded like this, just push forward on the pump to be ready.



    The endcap delivered is on the right, look online and you will find the version on the left for sale readily. Buy it.




    Adds plenty more room needed for spring coil bind


    3 rounds in the tube look like this with the stock follower shown



    Sticks out like this


    I used Dykem, but you can use a magic marker, scribe a line where the tube ends



    Trim away to the scribed line


    You get this


    The factory spring is cut by Safety Harbor to 22 coils... each coil is .050 in diameter.


    CAD a couple of spacers. Ended up using the .150 depth version.



    You see relief slots for the detent pin, and a slot to put the new spring/pin combo once made in metal. I cut the spring to 18 coils and stretched it out.



    Video of the result. Holds 3 in the tube now.


    https://www.youtube.com/watch?v=4w0QeJaewyw&app=desktop

    So how do you finish it?

    Sending the spacer file to shapeways to make in steel, and make a new detent using a 3/32 piece of brass rod and a small spring sourced from a gunsmith spring kit.



    The spacer is bastardized due to the heat from the printer bed so it's flex out wider than it should be. Also more important is the excess steel from the X-pattern will be machined away. That will cut the length of the cap back closer to being flush with the barrel.



    Once I have the spacer in metal and flycut the endcap, I'll be satisfied with my 3+1 shorty.

  2. #2
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    Nice project!

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    Registered User timkel's Avatar
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    Nice mod.

  4. #4
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    How many 1-3/4" shells? We need a fix for extracting the short shells.


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    Quote Originally Posted by strobro32 View Post
    How many 1-3/4" shells? We need a fix for extracting the short shells.
    I don't have any to try out.

    Saw some videos (one vid was showing a Serbu Shorty) where the main issue was the mini-shells would do a cartwheel when popped onto the lifter from the tube. The shell could land backwards on the lifter which is then chambered/failed. That put cold water on my hopes for them.

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    Sorry for the big pics

    I did some more tinkering after work today.

    Revised the dimensions (a little tighter on the ID & OD, and solid). I decided I would have them Shapeway'd solid and I could drill the pockets much more precisely on my milling machine afterwards.

    I made 3 thicknesses for testing. The heights were programmed at .180 .200 and .220

    They ended up with shrinkage at .160 .185 and .205



    I only tested using the .185 and .205 - also I lowered the print bed temp from 75Celsius down to 65C and the print nozzle from 210C to 205C and it made a much less distorted version than yesterday. The filament I'm using is 3mm ColorFab Ngen on a Lulzbot Mini printer.



    A brand new full size spring showed up that I ordered over a week ago. I should mention the new factory spring only measures .043 wire thickness compared to the .050 that came from SHF. Perhaps he uses an extra power spring? Regardless, the math on how many coils to use are different compared to the 1st post.



    I tried several variations of spacer and spring tension and settled on the .205 with 15 coils



    This video shows the last final round has plenty of force, and the 1st round out seems like normal on a stock 870


    https://www.youtube.com/watch?v=oACVXawxTYo&app=desktop

    So I'm now settled on a .205 thick spacer, 15 coils. The cap doesn't stick out much at all past the muzzle. Doesn't look too out of place.



    If I decide to not flycut the X-pattern off, the .205 (on my gun) turns out to line up well.

    Last edited by Hey...; 05-16-2019 at 11:48 PM.

  7. #7
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    Shapeways steel is hard to machine. I'm thinking aluminum; I'll send the .220 file size and if it's thicker than .205 I can always mill or sand it down to .205

    Then mill in the pockets.

    Another thing to mention is that 2 3/4 shells like any other cartridges all have different lengths. The wimpy bargain (Suprema) 00Buck is similar to #6 shot, but slightly shorter than Winchester Slugs. This mod fits most with ease but just barely fits 3 slugs; that's why I chose the largest spacer and the spring chopped as such.
    Last edited by Hey...; 05-14-2019 at 10:22 PM. Reason: chopped shorter than my dick

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    Registered User xdamagedx's Avatar
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    Quote Originally Posted by strobro32 View Post
    How many 1-3/4" shells? We need a fix for extracting the short shells.

    The trick is to use a OPsol adapter in the Mossberg version. The trick to the Remington version is this post (and use regular shells).

    Cool project.

  9. #9
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    Many years ago I ran across a post by a smith who detailed the mods needed to make the short shells eject on the 870 but I can't find it. So frustrating.

  10. #10
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    Went ahead and bought brass instead of aluminum. Not much more $ and more durable. I don’t want the little spring loaded plungers wallowing out the holes over time. I intend this mod to last as long as the gun does.

    This thread is on hold for a while until the spacer shows. I can drill out the holes the day it arrives.

    Last edited by Hey...; 05-15-2019 at 09:21 PM. Reason: guess

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    As a side note/update on the z-mag coupler... instead of sand casting I bought a lost wax casting set-up. More precise and higher quality than sand. All the supplies are sitting and waiting. The Corvette has been done a while now but guess what, I’m installing hardwood floors in my house... myself...so that sucks after a long day’s work to come home to that. My little casting hobby is on hold due to Life.

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    Registered User xdamagedx's Avatar
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    Quote Originally Posted by Hey... View Post
    As a side note/update on the z-mag coupler... instead of sand casting I bought a lost wax casting set-up. More precise and higher quality than sand. All the supplies are sitting and waiting. The Corvette has been done a while now but guess what, I’m installing hardwood floors in my house... myself...so that sucks after a long day’s work to come home to that. My little casting hobby is on hold due to Life.
    I'm Interested to see the results when you get around to it. Nice job with the KEG

  13. #13
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    Final installment.

    Shapeways delivered the brass spacer faster than they said.


    Compared to the plastic the dimensions are closer to spec.


    The brass ring is taller, because it's closer to spec (what my CAD drawing said it should be).



    Still need to make the detents, but a quick visual of what it would look like done.



    The drawing was .220 and brass turned out .218 and plastic shrank to .205


    Need to make a pocket not spring-loaded to lock the original detent into place.


    Here's a little trick. Mark with Dykem (or magic marker) and since the ring is .125 thick, I need to find the middle point of that.... set/lock your dial caliper to 1/2 the distance which in this case is .0625 and drag one jaw on the edge as the other jaw makes the scribed line.



    Pocket made. Time to move on to the spring loaded detent on the other side of the ring.




    In this case the spring-loaded detent is closer to the edge so I made the scribed line just south of the middle.



    Drilled


    DISCLAMER- I'm using brass rod because that's what I have on hand. The brass as a detent pin will wear out faster than steel. Wont last a lifetime. I plan to get some 3/32 steel rod to remake this at a later date.


    The spring I had as part of a misc gunsmith spring kit. I have an extensive selection of small springs from various kits I've collected. The brass rod was rounded (roughly) using a needle file and then smoothed using a buffing wheel.



    The section I need cut using a hacksaw, dress the cut edges afterwards.


    The detent sitting below depth. Gives me an idea how much spring I need. I chose to stand the spring in the gap, and add one coil, then make the cut.



    Ready to install. If this was the final steel spring detent I’d have made a notch on the body and staked it in place.



    Because the brass spacer was thicker I lost 1/4 thread on the end of the tube, that’s okay though because it’s insurance and space for a full 3 shells of various makes to fit. Luckily the end cap landed square. I ended up using a piece of flatstock (similar thickness to the spine of a butterknife) that fit the groove and used it to tighten hard into place. Actually, the endcap fully tightened is one single divot notch past where you see it, I loosened it that one notch to make it line up visually.




    She still has dried Dykem showing on both sides of her brass ring, the whore.


    Final pic. 3+1
    Last edited by Hey...; 05-28-2019 at 11:06 PM. Reason: Nothing to see here... move along..

  14. #14
    Registered User garandman's Avatar
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    Nice DIY 'smithing.

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    ^ Thanks.

    To endcap this thread, a quick video. Works great.

    00buck

    https://m.youtube.com/watch?feature=...&v=wwacXaJVhcU
    Last edited by Hey...; 06-29-2020 at 10:25 PM.

  16. #16
    Mr. Miata
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    I like the brass!
    AWWWW NUTS!

    REAL MEN DRIVE MIATAS

  17. #17
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    Yeah the brass denotes somethingís going on, but regular people have no clue.

    Went shooting with it 3 weekends ago. Nobody caught on. They were gun people but not nfa savy. Apparently all thought 3+1 out of a gun that size was normal. Not one question or comment. I mentioned it but didnít raise an eyebrow and zero questions.

    I was glad each time I fired the 4th round though.

  18. #18
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    I am amazed you can buy a piece of 3d printed brass like that!

  19. #19
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    Quote Originally Posted by Gaujo View Post
    I am amazed you can buy a piece of 3d printed brass like that!
    I know aluminum is printed. The brass and steel is printed in wax and they use that to make a lost-wax casting.

  20. #20
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    Would it have been simpler to make the brass piece on a lathe vs printing?

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