AR 7.62x39 Upper Build Questions

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Putting together a 7.62x39 upper just for kicks and because I already have another rifle in that caliber.

Decided to go with a carbine length gas system and a 16 inch barrel and have a decent bcg, upper, gas tube, and barrel already.

What I would like to know from those who built one, did you use an adjustable gas block, if so what brand etc., second, what sort of buffer (carbine, H1, etc.) did you use, and last, did you use one of the 7.62x39 specialty firing pins (like Red X, Model 1, or Black Rifle) and/or the Wolff extra power spring. If anyone has used the Rubber City or Sun Devil adjustable gas key, that is something else that might substitute for the block. Waiting on upper handguard until I settle the gas block question.

FWIW, I've used the Odin Works adjustable gas block on a 6.8 SPC build and have been pretty happy about it but I am open to others. This is not a competition upper so I am not worried about tailoring the gun for each type of ammo--probably just find out what it likes and then not twiddle with the gas block or adjustable gas keysetting.

Appreciate any pointers here.

 

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I built mine with a standard lo-pro gas block (carbine length), on a yankee hill machine 16” barrel. I used AIM Surplus 9310 nitride BCG with their enhanced firing pin and an H2 buffer. I have a LaRue MBT trigger in it and have had zero problems outside the common issues within the first 10 rounds of everything settling in. I have about 1,000 rounds through it by now, just put about 300 rounds through it last weekend.

 

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I like the benefit of the H2 buffer as it allows some more dwell time in the unlocking to help with bolt lug life, an adjustable gas block would help with this as well, but for my x39 I went with simplicity in a fixed gas block.

 

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I like the benefit of the H2 buffer as it allows some more dwell time in the unlocking to help with bolt lug life, an adjustable gas block would help with this as well, but for my x39 I went with simplicity in a fixed gas block.

Thanks. Did not know whether an adjustable gas block was necessary for this for reliable function or not and the buffer weight helps as a starting point if I go the convention route. Is your bcg an AR15 type or the M16 type with the full tail if you don't mind me asking?

 

[someguy2800]

I have an adjustable gas block on mine but only because I had the upper built as a 300 blackout and I converted it over to 7.62x39. It just a cheap one I bought off etsy and is not very nice, but does function. Mine has an A2 rifle stock on it and the buffer is actually empty (no weights inside). If your using an AGB anyway I wouldn't fret over the buffer weight. I use the same lower for my 223 varmint upper.

Mine functioned fine with the standard firing pin for the first couple hundred rounds but I bought the enhanced firing pin from black rifle arms anyway. I also got a wolff extra power hammer spring but after installing it and finding it increased my trigger pull weight by like 2 lbs I put the factory spring back in and threw the wolff in the drawer. I have never had a missfire.

 

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Really appreciate the info. Thanks. Did not know etsy sold AR stuff.

 

[someguy2800]

Yeah it was like $30. I figured I would give it a try and then eventually replace it with a decent one but its still trucking. I was still learning the ins and outs of AR's so I didn't want to invest in a bunch of high dollar stuff that I didn't know if I would like or not.

 

[carbine85]

I built mine with a Faxon mid length barrel, Slick side upper, Aim bolt carrier, Acme cheapo adjustable gas block, H2 buffer. I've never had a problem.

 

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I built mine with a Faxon mid length barrel, Slick side upper, Aim bolt carrier, Acme cheapo adjustable gas block, H2 buffer. I've never had a problem.

Did your adjustable gas block use set screws? Heard that set screws can get locked into place-which for me is not a bad thing--just don't want them loose.

 

[<*(((><]

Thanks. Did not know whether an adjustable gas block was necessary for this for reliable function or not and the buffer weight helps as a starting point if I go the convention route. Is your bcg an AR15 type or the M16 type with the full tail if you don't mind me asking?

I always buy the fully shrouded portion around he tail, but lots of people don’t fret over the difference, in a civilians rifle I don’t think the difference will ever be known. I just like the added insurance so to speak.

 

[carbine85]

Did your adjustable gas block use set screws? Heard that set screws can get locked into place-which for me is not a bad thing--just don't want them loose.

It has 2 set screws. I used a small amount of Blue Locktite. Acme outs them on sale all the time for like $25/

 

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It has 2 set screws. I used a small amount of Blue Locktite. Acme outs them on sale all the time for like $25/

Thanks. That is not much more than a plain gas block.

 

[AndyP]

Putting together a 7.62x39 upper just for kicks and because I already have another rifle in that caliber.

Decided to go with a carbine length gas system and a 16 inch barrel and have a decent bcg, upper, gas tube, and barrel already.

What I would like to know from those who built one, did you use an adjustable gas block, if so what brand etc., second, what sort of buffer (carbine, H1, etc.) did you use, and last, did you use one of the 7.62x39 specialty firing pins (like Red X, Model 1, or Black Rifle) and/or the Wolff extra power spring. If anyone has used the Rubber City or Sun Devil adjustable gas key, that is something else that might substitute for the block. Waiting on upper handguard until I settle the gas block question.

FWIW, I've used the Odin Works adjustable gas block on a 6.8 SPC build and have been pretty happy about it but I am open to others. This is not a competition upper so I am not worried about tailoring the gun for each type of ammo--probably just find out what it likes and then not twiddle with the gas block or adjustable gas keysetting.

Appreciate any pointers here.

I have built a handful in this caliber. H2 buffer works great, on rifles that will have a suppressor on or off I used SLR adjustable gas blocks. I always put a RedX pin in this caliber. The stock hammer spring will fire most russian ammo but there are a few brands that have harder primers. The Wolf spring is a fix, but it also increases the trigger pull- I personally put Gieselle triggers in mine. 3.5lb triggers yet with a stronger spring that will light anything. Last thing... stick with C- products defense mags.

 

[boom boom]

I have built a handful in this caliber. H2 buffer works great, on rifles that will have a suppressor on or off I used SLR adjustable gas blocks. I always put a RedX pin in this caliber. The stock hammer spring will fire most russian ammo but there are a few brands that have harder primers. The Wolf spring is a fix, but it also increases the trigger pull- I personally put Gieselle triggers in mine. 3.5lb triggers yet with a stronger spring that will light anything. Last thing... stick with C- products defense mags.

Thanks. The RedX is an easy fix so I ordered one. Ordered some C Products 10 round magazines as those seem to be fairly bullet proof and reliable from yours and others information.

Thanks for the SLR reference. They have some interesting stuff on their website. Likewise thanks for the info on the H2 buffer--I really hate to have loose parts hanging around from buying the wrong buffer via trial and error.

All in all, I prefer a rifle that doesn't beat up the brass in case I want to reload for it. Did so long ago for a Russian SKS using Tech Sights. It had significantly better accuracy than the steel stuff using H 4198 and Hornady bullets. But the SKS really beat up the brass.

Idle parts become new builds even if all you have is a spare buffer which leads to a buffer tube and so on.