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Thread: Tube gun from scratch

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    Self-Proclaimed Armorer bloodsport2885's Avatar
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    Default Tube gun from scratch

    I've been looking through the subgun BIY and it got me wondering if anyone else has ever built thier own subgun (semi) from scratch or mix and match parts. I have a running idea and sketches for a sub caliber carbine that uses AR15, sten, sterling,grease gun, and other subgun designs to produce a sub-caliber plinker. Has anyone else ever tried to make a bolt and receiver set from scratch and adapt parts to work?

    My idea uses an AR15 FCG, upper tube receiver, lower square channel receiver, and some custom made parts. The barrel is retained like the AR barrel with a large threaded nut and an indexing pin in the barrel (although if its just a plinker and sights are mounted on the receiver it may not matter about indexing the barrel). Its also possible to build a pistol using another smg barrel if that route proves to be easier, or use a simple wire folding or non-folding stock made from bent 1/2" round bar and put the receiver on an F1.
    Hold Mah Beer and watch this sh*t.

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    Gunco Member Bullpup's Avatar
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    not a tube gun, well maybe square tube, but very scratch built:
    Weaponeer Forums

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    THE 9mm ADDICT MUSIBIKE's Avatar
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    It has all been done for STENS and various others.

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    Self-Proclaimed Armorer bloodsport2885's Avatar
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    Quote Originally Posted by MUSIBIKE View Post
    It has all been done for STENS and various others.
    But good sten kits are becoming more and more rare. Plus I'm thinking about, what if the ATF and Congress decide no more imports at all. By using known firearms designs you make the project much smaller and easier because this introduces constants. Constants that would otherwise require months of research/dangerous trial and error. If you take the weight of another 9mm smg bolt and replicate it and its recoil system, you basically transplant a design that you can trust to some extent. There is also the fun factor. Building your own firearms from scratch is what this forum started out for.
    Hold Mah Beer and watch this sh*t.

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    GuncoHolic kernelkrink's Avatar
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    One of the problems inherent in converting an open bolt SMG to a closed bolt semi is a lot of subguns use what is known as "advanced primer ignition". An open bolt smg commonly has a firing pin machined into the breechface, as the bolt chambers a round and closes on it, the pin dents the primer and sets it off before the bolt is fully forward. We're talking a fraction of an inch here, but that adds the forward momentum of the bolt to the weight of bolt/recoil spring equation when it comes to figuring what is needed to keep it closed long enough for the pressures to drop. Some designers may have been walking the very edge of what is "heavy enough" and when the forward momentum is removed from the equation it comes up a bit short.

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    Self-Proclaimed Armorer bloodsport2885's Avatar
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    Quote Originally Posted by kernelkrink View Post
    One of the problems inherent in converting an open bolt SMG to a closed bolt semi is a lot of subguns use what is known as "advanced primer ignition". An open bolt smg commonly has a firing pin machined into the breechface, as the bolt chambers a round and closes on it, the pin dents the primer and sets it off before the bolt is fully forward. We're talking a fraction of an inch here, but that adds the forward momentum of the bolt to the weight of bolt/recoil spring equation when it comes to figuring what is needed to keep it closed long enough for the pressures to drop. Some designers may have been walking the very edge of what is "heavy enough" and when the forward momentum is removed from the equation it comes up a bit short.
    Thats why using a closed bolt system measurements like the Colt smg will give you accurate info. Its essentially operating on the blowback principle which will run any hammer-fired pistol caliber carbine.
    Hold Mah Beer and watch this sh*t.

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    BHP
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    Gunco Member BHP's Avatar
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    As a type 07/02 I have been planning an open bolt 10mm with some features of the CZ26 and a layout similar to the Beretta PM 12. If it works I had planned to build a semi variant but I haven't gotten into the semi design phase yet. FA first, SA somewhere after that.

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    Gunco Member deth502's Avatar
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    there have been alot of sgn 9 build going on since the article came out. that seems to fit your criteria. im working on a spin off of it. the build itself is posted on other sites. ill post pics here when its done.

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    gregolver greg's Avatar
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    cant do a open bolt, has to be a closed bolt, or the feds will get you
    gregolver

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    THE 9mm ADDICT MUSIBIKE's Avatar
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    Quote Originally Posted by greg View Post
    cant do a open bolt, has to be a closed bolt, or the feds will get you
    This is correct. An open bolt semi new build is no longer allowed in the USA.

    Any semi must fire from a closed bolt which has a separately driven firing pin.

    And, a tube build to support an open bolt firing system is considered a MACHINE GUN.

    Look at your cards good before you play the hand!

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