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Thread: AR/AK hybrid trunnion and bolt

  1. #1
    TRX
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    Default AR/AK hybrid trunnion and bolt

    If you want to build an AK-ish rifle with minimal AK parts, you're limited to blowback, or you have to use an AK trunnion, bolt, and bolt carrier. Those are all fairly complex parts to DIY.

    I was looking at an exploded view of an AR-15 last night. The barrel screws into a "barrel extension" which looks like a simple stepped bushing; threaded for the barrel at one end, locking lugs in the other. I assume it's pressed into the upper receiver; I've never had an AR apart.

    You could press an AR extension into a simple block and then you'd have a threaded front trunnion with locking lugs, that an ordinary AR bolt would lock into.

    The AR bolt carrier wouldn't work at all. You'd have to make an AK-ish carrier from scratch... it might be possible to do the carrier as a weldment, and cut the cam track all the way through with a Dremel instead of an internal track like an AK.

    I have no idea about the barrel diameters of an AR, but adapting the RSB and GB wouldn't be a big deal.


    I present this as a thought experiment; it would be more work than it's worth as long as AK trunnions, bolts, and carriers are affordable, unless you just wanted to avoid imported AK parts as much as possible.

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    GuncoHolic kernelkrink's Avatar
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    On the AR the bbl extension is threaded onto the bbl by the manufacturer and is not normally removed after that. It is made that way as a manufacturing expedient, you can machine the locking lugs and such a lot easier witrh access to both ends. The smooth exterior of the extension is a slip fit in the AR upper, there is also a locating pin and a slot in the upper to align the two components. A large nut then threads over the bbl mounting area of the upper, retaining the bbl. Don't have the dimensions handy, but the Ar bbl is so big at the rear I doubt you would have much trunnion left after drilling it out to fit the bbl.

    If you really wanted to use the Ar system in an AK, you could cut off both an AK carrier and an AR carrier and weld the two together, then use the stock AR bolt.

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    tired of idiots vz58's Avatar
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    the ar barrel extension is .998" od
    the receiver is .999-1.000

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    Gunco Veteran Viper Dude's Avatar
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    My two pennies here...
    I have turned down AR-15 barrels to 23mm removing the locking lug rear section with a carbide lathe bit. The resulting barrel will fit an AK trunion. The AK RSB will be a bit too large for it without a bushing.

    As proposed a simple custom AK trunion machined to the AR .990 inch barrel can retain an AR barrel locking lugs and all. The AK cross pin actually goes through the softer barrel area rather than the hardened locking collar !!! Resulting positioning comes very close to stock AK.

    The trick part needed is a clone AR-AK bolt. Perhaps Kernel Krink's clone carrier is a simpler solution.

    VD

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    gunco irregular moleman's Avatar
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    It might be easier to just make an ar15ish style gun out of 1" I.D. tubing. Kinda like the ar15 meets the SGN-9 style. You really would only need an: ar15 barrel; bolt; FCG(a remington 870 fcg would also work and speed up the build); buffer and spring. To keep it simple you could just use the direct inpingement or you could get fancy and put a piston in it. To make the mag catch I'd use the flapper style that is on the galil ar15 mag adaptors.

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    Gunco Veteran Viper Dude's Avatar
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    Hello moleman,
    A tube gun !!! Gotta do something with that darn gas key. Maybe make it recoil operated with a cocking handle on the side... a .223 Johnson rifle !!! That's back where it all started years ago.

    A more radical tube type design could use the Reising system. A prototype of that system was built as a 7.62 NATO rifle by Eugene Reising.

    Maybe we need a clean sheet of paper.

    VD

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    gunco irregular moleman's Avatar
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    VD, The first time I looked at a johnshon LMG I thought that stoner had stolen that as the basis for the m16. I haven't messed around with recoil operated guns enough to figure out an easy way to make one. For the gas key/piston on the ar15 tube gun you're right, you'll need to mill a slot in the tube and weld on a channel. A side charger would make it an easier build and a pivoting break in the receiver tube like an ar does(with a gas shield welded to the stock portion to shield your face from the back of the key slot). The ar15 strikes me as a tube gun that just happens not to be round on the outside. The home made ar15ish tube gun build is on my list of builds to do along with a dozen others. Luckily I have extra ar parts gathering dust out in the garage.

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    Gunco Veteran Viper Dude's Avatar
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    Hello moleman,
    Stoner worked with Mel Johnson to develope the AR-10 rifle which later was morphed into the M-16 & AR15 rifle.

    VD

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    TRX
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    I mentioned my idea over on homegunsmith, and someone has already built a bolt-action rifle with an AR bolt and barrel extension. They were even talking about it this morning.

    That's me, a day late and a dollar short...

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    Gunco Veteran Viper Dude's Avatar
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    Hello TRX,
    A gunsmith/mfg friend has already experimented with the steel tube AR idea. However he keeps such things secret for business reasons.

    Perhaps the gas key solution is to eliminate that darn gas system all together. An op-rod could be used under the receiver tube as was done with the model 50 Reising. A fork like op-rod passed on either side of the magezine to connect with the bolt behind the magwell. Thickwall steel tubing kept the receiver rigid.

    VD

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