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Thread: Beretta AR70/90 build

  1. #1
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    Beretta AR70/90 build

    Started this build a while back, and have come a long way since. Still not happy with my form dies yet but hopefully this week they'll be ready for the prime-time!

    Beretta AR-70/90, the nicest looking black rifle I can think of:





    So I had to have one.

    Bought a kit, got started, here's the progress from last week:



    Got my flats drawn up and repair tabs made, and started getting enough made up to go on my website. Dies were next on the list...but I'm up to revision 4.5 and the dies are still cutting the flats at the bottom edge of the ejection port 3 out of 5 times.



    Trunnion repair is pretty easy once you figure out fixtures to hold the tabs back on. I made them out of 4130 to make welding them to the hardened trunnion a little easier. By TIG welding with ER80S-D2 rod, I'm able to get enough heat to make a solid full-penetration weld fast enough to be able to keep the trunnion cool enough, and still get enough heat into the 4130 to get a little air hardening action going on. The trunnions are not near full hardness, but after welding they're pretty close to RC30-32 between the weld and the pin hole. At the same time, I was able to keep the trunnion cool enough to be able to hold it in my hand-almost. Could still maintain a 2-count hold, so the heat treatment in the locking lug area was as unaffected as it's going to get.



    Rear takedown blocks were next-and you can see in one of the photos above I've got a rough blocky one finished up for dimension testing and I have some nicer finished ones about ready. Between flats, blocks, and trunnion tabs, the only parts left to make is the internal receiver rails and the full-auto denial parts. Both are drawn, prototypes made to proof the prints, and a few detail items have to be finished up before I can assemble my first upper receivers.

    After the receivers are done I've got some barrel blanks here that are going in the lathe for barrels. I need to make two for myself, and I'm trying to work with Criterion and Green Mountain to supply barrels. I hear Mark Serbu is also going to be doing barrels at some point.

    I'll post up some more photos of my build as soon as I get more done.

    If some of you need parts for your build, check out http://jtmachineservices.com for the parts I'm making. I'll be adding more parts and getting things stocked in the next two weeks-the initial Reddit flood of orders has nearly wiped me out!

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    Had an end mill blow out and damage the version 4.5 lower die insert early this evening, so had to start over on that part of the die.

    Setting up and skimming the top of the insert blank to make sure I start flat:



    About halfway done, getting ready to start the tab indentations



    More tomorrow evening, if I get time to work on it. It's going to need some attention around the raised oval boss. (which does nothing, come to find out, I have no idea why it's in there)
    Last edited by Xnke; 09-11-2020 at 03:30 AM.

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    Nice work. Keep us updated

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    Looking forward to your progress.
    The embossed oval is allowing room/capturing the front pushpin retainer spring. I have not found detailed picture of what the spring actually looks like.
    If I were to guess I can picture a spring with outward ears on the open end, when squeezed together, inserted into the oval area and let go. The spring pressure retains the spring. Obviously the spring is bent in such a way that a pushpin when inserted it is also captured.
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    Last edited by 21HK; 09-11-2020 at 10:16 AM.

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    Quote Originally Posted by 21HK View Post
    Looking forward to your progress.
    The embossed oval is allowing room/capturing the front pushpin retainer spring. I have not found detailed picture of what the spring actually looks like.
    If I were to guess I can picture a spring with outward ears on the open end, when squeezed together, inserted into the oval area and let go. The spring pressure retains the spring. Obviously the spring is bent in such a way that a pushpin when inserted it is also captured.
    You can see the clip in the photo of the repaired trunnion-it doesn't get up anywhere close to the raised oval up on the side of the trunnion. I am assuming the retainer clip for the pushpin spring was destroyed during the torch cut, because I have not found any evidence of anything living in that divot other than the little snowman spring.

    I've reached out to some Italian guys who have their semiauto versions to see if there is a little clip/spring/piece that needs to go in that during assembly-if so I'll have to make that as well!

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    Looks like I popped in here after a few months away, just in time for this build. Nice work.

    Is the flat laser cut (or water jet?)(not that it matters, really, I'm a CNC Programmer/machinist, so it seems a relevant question to me) Much better looking than the Cold Steel 80s from several years back

    Nice work! I got a new CC burning a hole in my wallet.

    I guess I should lookup one of these kits? I haven't seen any available in a couple years or more. Numerich had them at one point 3 years ago, and I almost bought one but waited too long. They were sold out by the time I got around to ordering
    They who can give up essential liberty to obtain a little temporary safety, deserve neither liberty nor safety.Ben Franklin.. 1775

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    Senior Veteran The War Wagon's Avatar
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    Question

    Very sharp. Where does one find the parts that DON'T need rebuilding/hand-crafting for one of those?


    p.s. - does she come with the rifle?


    Last edited by The War Wagon; 09-12-2020 at 05:39 PM.
    We have no government armed with power capable of contending with human passions unbridled by morality and religion. Avarice, ambition, revenge or gallantry would break the strongest cords of our Constitution as a whale goes through a net. Our Constitution is designed only for a moral and religious people. It is wholly inadequate for any other. - John Adams, 2nd U.S. President -

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    Quote Originally Posted by slim View Post
    Looks like I popped in here after a few months away, just in time for this build. Nice work.

    Is the flat laser cut (or water jet?)(not that it matters, really, I'm a CNC Programmer/machinist, so it seems a relevant question to me) Much better looking than the Cold Steel 80s from several years back

    Nice work! I got a new CC burning a hole in my wallet.

    I guess I should lookup one of these kits? I haven't seen any available in a couple years or more. Numerich had them at one point 3 years ago, and I almost bought one but waited too long. They were sold out by the time I got around to ordering
    These kits just hit the US this summer-they have never been available before. Not the same rifle as an AR70/.223!

    So far Bullfrog Corner has had the cheapest kits, but if they don't have them Apex has some, Century arms brought some in, Elk Country on Gunbroker has some, RTG parts has some, and several other importers have bought some.

    My flats are laser cut 1018 P+O steel sheet, and trunnion repair tabs are laser cut 4130 alloy sheet. Rear takedown pin blocks are CNC 1018, and the internal rails are probably going to be investment cast steel, finish machined. I can't get the cost of manufacture low enough to be economical machining them from solid so far.

    The kits so far have been in really good shape, even the plastic furniture is pretty nice. I have obtained three kits so far, two are identical and the third (the first kit I bought) is slightly different. Very few parts interchange with the AR70/.223, and no parts are an "exact" interchange.

    War Wagon, She doesn't come with the rifle, but the rifle she's holding is not the one that came to the US. That folding stock on her rifle so far isn't available here, and a single original folder sold on Gunbroker for north of 2200$.

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    Senior Veteran slim's Avatar
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    I'm glad you cleared that up for me, sir

    Thanks for the vendor suggestions as well. I'm on it.
    They who can give up essential liberty to obtain a little temporary safety, deserve neither liberty nor safety.Ben Franklin.. 1775

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    Quote Originally Posted by Xnke View Post
    War Wagon, She doesn't come with the rifle, but the rifle she's holding is not the one that came to the US. That folding stock on her rifle so far isn't available here, and a single original folder sold on Gunbroker for north of 2200$.
    Eeep.

    There's a guy on Barfcom who MADE a folder for his kit (I didn't save the link, but google-fu should find it for you), that was pretty ingenious.

    Ya' know what - I just went back and found it. Check out how he made HIS folding stock!
    Last edited by The War Wagon; 09-13-2020 at 05:56 PM.
    We have no government armed with power capable of contending with human passions unbridled by morality and religion. Avarice, ambition, revenge or gallantry would break the strongest cords of our Constitution as a whale goes through a net. Our Constitution is designed only for a moral and religious people. It is wholly inadequate for any other. - John Adams, 2nd U.S. President -

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