Another replacement barrel trunnion thread!
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Thread: Another replacement barrel trunnion thread!

  1. #1
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    Another replacement barrel trunnion thread!

    The other thread is almost 2 years old without any progress, so I'm working on it myself. I gather there may be a few parties pursuing the production of a lightweight non-QD trunnion as many are as frustrated as I am. I figure, if someone beats me to it, I'll get one and I win. If they don't, I'll make one and I win. No downsides.

    I'm about 90% done with measuring and modeling it. The goal is not to replica a stock trunnion to include tolerances it was made with, but to correctly assess the original planned dimensions and tolerances of which all the trunnions fall within. I'm happy with how the measuring is going and confident in the assessment of most of the measurements and their tolerances. That said, I'm also somewhat obsessive and would like to be certain of everything.

    To that end, I wanted to have a sample set greater than 1 to be sure. Bushmaster is out of stock, so I'm asking other members. Will any one or two of you loan me your trunnion for a week? I can cover shipping and a loaner fee, or provide a free Magpul full auto ACR lower, or work out some other arrangement.

    If your willing to do so in the interest of furthering this project and putting an end to the wait, please let me know. Thanks!

    PM or email me at hkbeltfed@yahooNOSPAM.com just remove the NOSPAM part.

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  2. #2
    I like Turtles bigdog2003_99's Avatar
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    I have a trunion you can borrow. I'll email you too man.
    Rest in Peace Franny
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  3. #3
    Moderator BanditBuzz's Avatar
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    Wow...please keep us posted. I would be very interested in picking one up.

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  5. #4
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    email sent

  6. #5
    Full Member 10Industries's Avatar
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    I don't hear any machining going on in here.....

  7. #6
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    Interested to see what happens with this.

  8. #7
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    Many thanks to Anyonebutme.

    It's done, moving forward...

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  9. #8
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    Must ... Wait ... Patiently ...

  10. #9
    Moderator BanditBuzz's Avatar
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  11. #10
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    I gave the machine shop the final file, tolerances, and ok to proceed on Monday morning. I only have the funds to do 5 now at about $300 each. It gets cheaper with quantity, but I'm not going to fund it. So, with one each for Big Dog and Anyonebutme, and one (maybe two) for me, that leaves one (two at most) for Gun Broker. If I do another run, it will have to be prepay, a larger quantity to get my cost down, and still sell them for $300+.

    This is just for the trunnion in 7075 with a milspec hardcoat anodize and to some fairly tight tolerances. Compatible barrel nuts and wrenches can be inexpensively purchased from Aero Precision. Longer term, I have a locking barrel nut planned, but other than the features needed to incorporate it into the trunnion, I haven't started it yet.


    The 3 stock trunnions I measured were all over the place and loose. I used the Ar15 ordnance print tolerances where applicable and fairly tight tolerances on the rest. That said, the shop said even if I gave them +/-.01, the finished result would be closer to +/-.001 anyway. They're also saying 4 - 5 weeks. The model has a few differences from the pics I posted and one of them is crucial as it's a real differentiator.


    Wish me luck!

    On a side note, that other trunnion thread is pretty disappointing with no progress after almost 2 years, what appears to be impractical features for machining in the drawings posted, and an unrealistic projected price (or a price based on an unrealistic volume or out of China)... unfortunately, it reminds me of the metal lower thread too
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