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AR Pistol in 7.62x39mm

Discussion in 'Rifles' started by Maverick44, Jan 4, 2020.

  1. james.long48

    james.long48 Active Member

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    https://www.blackriflearms.com/762x39-Melonite-QPQ-Bolt-Assembly-_p_239.html

    Here it is, bought this thing, been flawless since. Worth the price, breaking that extractor arm sucks. I keep my rebuilt kak bolt and a spare extractor arm in my grip.

    Definitely build your own, you get exactly what you need.

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  2. TreyG-20

    TreyG-20 TGT Addict

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    I had a BCA upper with an out of spec gas port. Sent it back to them and never heard from them again. Multiple emails and phone calls and nothing. Had to dispute the charge on my card in order to get my money back. Never again for me, but good luck if that is route you choose.
     
  3. zackmars

    zackmars Well-Known

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    A friend had a BCA barrel in 5.56 on a cheap build. It had a very tight chamber. Have seen a few BCA's with non-concentric threads

    Spend the money on a faxon.

    Also, BCA at one point got raided by ICE. There are better companies out there

    https://abc11.com/5122017
     
  4. Maverick44

    Maverick44 Certified All-American Gun Nut

    After some thought, I decided to stick with the Faxon barrel. I think I finally have the build where I want it. As soon as I get paid, I'll order the stuff and post the specs.

    I think for the price, it's going to be a very nice little set up.
     
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  5. AZ Refugee

    AZ Refugee Active Member TGT Supporter

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    Sep 23, 2014
    I built a 16" 7.62x39 with a stainless Bear Creek barrel, the chamber was incorrect. they sent me a new one, not issues since then.
     
  6. Maverick44

    Maverick44 Certified All-American Gun Nut

    I made my final decisions, and I ordered everything. Hopefully I'll have a working gun by this time next week. :D

    Here's the parts list.

    LOWER

    Spikes Tactical Spartan stripped lower
    Palmetto State Armory lower build kit
    - SB Tactical SBA4 pistol brace
    - PSA lower parts kit with enhanced polished trigger
    - Magpul MOE grip and trigger guard
    - PSA Carbine buffer tube, spring, and buffer
    H3 buffer (was not branded, but I believe it's a Bravo Company buffer)
    C-Products 30rd 7.62x39 magazine

    UPPER

    Spikes Tactical assembled upper (I think)
    Faxon 10.5" 7.62x39 Gunner barrel
    KAK Micro Slim Line Flash Can
    Seekins Precision adjustable gas block
    Spikes Tactical carbine melonite gas tube
    Midwest Industries SLH M-Lok 10.5" handguard
    Toolcraft 7.62x39 BCG
    Aero Precision charging handle

    I'm going to take the Vortex Strikefire II RDS off of my 5.56 AR and stick it on this one. The 5.56 is probably going to get a Primary Arms SLx 1-6x24mm SFP scope at some point. Until then, It'll be kicking around with irons.
     
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  7. Charlie

    Charlie TGT Addict TGT Supporter

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    Kerr County
    Waiting for the build pics, the final pics, and the range report! Hurry up! :green:
     
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  8. Maverick44

    Maverick44 Certified All-American Gun Nut

    Well, everything shipped and should be here before the end of next week. I went ahead and bought a go gauge to test the headspace on it. I'm too much of a cheap bastard to buy a no go and field gauge too, but there's an easy way around not having those as long as you have the go gauge. I'll update the thread with pics of the build and a range report once I get all put together.
     
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  9. Maverick44

    Maverick44 Certified All-American Gun Nut

    I got everything for the upper yesterday, so I went ahead and got that put together.

    Here's my setup. An old troque wrench, some cheap action vice blocks from AR Stoner, and one of those work benches/saw horses that can be used as a clamp. It worked OK. It would have been a little better if I had used an actual bench vise, but I don't have one. The blocks had a tendency to want to twist out of the work bench a little when you torqued down the barrel nut. They never actually came loose though.

    d0031ffe85c02e52c6295398741d42d1.jpg

    f2f3fed98ccad871ed406d4efb26cd90.jpg

    I chose to use Super Tech Moly Lithium Extreme pressure grease on the receiver extension/barrel nut. From what I understand, it's graphite free, and I already had half a tube lying around. There's a lot of debate over what works and what doesn't. The purists out there insist on Aeroshell 33 ms. Others say anything that doesn't have graphite in it is good to go. Some say the issues with graphite are exaggerated or even non existent. I don't know, after about 30 minutes of reading forum posts arguing over the issue, I was done with it. What I used is Moly, and is graphite free. That's good enough for me.

    The barrel nut instructions specified 40 Ft-lbs, so I cranked it down to that and broke it back loose 3 times to make sure the barrel was fully seated (I believe it also seasons the threads).

    606dafb2e77437595d738509e125eb85.jpg

    The nice thing about this barrel nut is that it doesn't have to be timed to work with the handguard or the gas tube.

    The gas block and tube were a breeze. Using a pencil, I marked the outside limits of the gas holes on both the barrel and the block, and then just lined them up. The hole on the block is slightly larger than the hole in the barrel, so you don't have to be absolutely perfect. There is some play. I used blue Loctite under the gas block, and on the screws. I don't do mag dumps, so it should hold. The barrel does not have divots, the gas block is held by the screws. They are in there tight enough that they probably marked the barrel. Going in later and drilling a couple of divots wouldn't be much trouble. I'm not going to do that until I know the barrel is good though.

    22fa41fc313b4f544174eb6a4f3cfd0b.jpg

    Next was the flash can. I like the look this thing has with a full length handguard. It just screws right on. You don't need a crush washer or anything unless you want to time it a certain way. The cut outs on the end did not end up being timed to where they were perfectly vertical or horizontal. I'm not sure if that bothers me enough to get a crush washer to fix it. You don't really notice it that much.

    73d6b7165d390f1767527996c77ecbe1.jpg

    Finally, the handguard. This thing is like air. It's stupid light, and beautifully machined. It's a tight fit on that flash can too. They don't touch, but there's very little room between them. It's a friction fit handguard, but seems to be a very well designed one. It locks onto the barrel nut and around the receiver pretty tight. That, along with the textured surface on the barrel nut, and how much it clamps down on that but should keep it from walking loose.

    I'll have to take it back off when I adjust the gas block, but that's pretty easy to do.

    It's so tiny. :D

    2fee9898c1e9bebb8e12b35861efb202.jpg

    And finally, the sight. I'll put some Magpul MBUS's on it too eventually. I have a magnifier for that RDS, so I'm going to use to to help test the accuracy of some loads I made up for the gun. Once I'm happy with that, I'll probably move the RDS farther back on the receiver.

    Oh, and this mag is kinda weird. I'm not used to that much curve. I stuck it in one of my other ARs, and it might take a little getting used to. It seems very well made though.

    508aa3f4eefc6171375a0932b234c6e5.jpg

    The lower parts showed up today. I'll probably put that together tonight. :D

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    Last edited: Jan 22, 2020
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  10. Maverick44

    Maverick44 Certified All-American Gun Nut

    I got the stuff for the lower in, so I got that finished up tonight. I think just about everyone here has either put an AR lower together, or has at least seen it done before, so I'm not going to bore you with that. The lower is just your run of the mill lower. The only thing special is the buffer. I went with an H3. From what I understand, this will help keep the bolt locked longer, and allows the pressure in the barrel to drop more. It's gentler on the bolt if that pressure is kept low. Broken bolts are a common problem with 7.62x39 ARs, so this, along with the adjustable gas block should hopefully alleviate that problem. If I need to go heavier, I can get a extra strong buffer spring. If I need to go lighter, I can swap some of the tungsten weights in the buffer for steel weights.

    The black one is a standard PSA carbine buffer, and the Gold one is an H3 (three tungsten weights).

    0c021831a882e0222eae28be67e511af.jpg

    Once I got the lower put together, I tested the headspace.

    The ejector needs to be removed from the bolt to test headspace properly, Which was kind of a PITA to do (taking it out is the easy part, putting it back is not so easy). I basically stuck a empty case in a vise, used it to push the ejector in to reduce the pressure on a pin, and did a balancing act where I held pressure on the case, held a punch in that same hand, and used a small hammer to careful drive the pin in/out.

    With my headspace gauge, removing the extractor was optional. It made the process easier, so I just removed it.

    5653c06248fa75b153508f7b39aa19b4.jpg

    The gauges are not that cheap (about $30+ each), so I made due with just the go gauge. This tests the minimum headspace. A trick you can use is to use masking tape on the back of the gauge to increase it's length. The tape I used was about 0.04" thick. From what I understand A no go gauge (max headspace) is between 0.03" - 0.06" longer than a go gauge for 7.62x39. A field gauge is about 0.10" longer than a go gauge. If a gun fails a field gauge test, it is not safe to shoot at all.

    f5cebc72d29cd123aee6180c262afd7e.jpg

    With the go gauge, the bolt closed without any resistance.

    c1982b4e8111549515c8f848b2764526.jpg

    With one layer of tape (no go length), the bolt barely closed, and did not close easily. It had to be forced close. I believe it is relatively normal for ARs to do this on a no go gauge.

    Had the tape been just a tiny bit thicker (0.01" - 0.02"), I doubt it would have closed.

    This is where it met a lot of resistance

    f18627b9b8e90cc4e4c6c620a3744526.jpg

    With 2 layers of tape (not quite field gauge), the bolt would not close period. Not even close. The gun is safe to shoot and is within spec.

    A range report will hopefully be coming soon.

    5445a3cf6346cfe4c523abd4c65a2c90.jpg

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