Help me build my new 7.62 x 39 Ar

parttimer · Nov 30, 2015

I figured I would check with the MDS brain trust before I start buying parts. I am putting together a 7.62 x 39 AR. I figure with holiday sales I should pick up some parts while the parts are at discounted prices.
The rifle will be used for casual range shooting (less than 1000 rounds a year) and maybe at some point in the future some 3 gun comps.
I am also looking to run it suppressed at some time in the future.
I would like to have this set up so I don't have to change things in the future when I run it suppressed or do some 3 gun shooting comps. It will probably be ceracoted as part of the build.

So far a have:
Billet Engage upper and lower
16" YHM barrel http://yhm.net/yhm-76-tf.html
Magpul MOE butt stock (mil spec) and grip.
PEPPR mount
Bushnell AR optics 1-4 scope.
I need everything else.

BCG - is there a certain brand that is really where its at? I know I will need and extended firing pin to run steel cased ammo which is what I will feed it most often.

Hand guard - I was looking at the Midwest industries SSK 15" . It is a free float one piece lightweight rail key mod system. Should I be looking at a m-lok rail? Will a 15" rail create problems for an adjustable gas block? Are there any other lightweight rails that I should be looking at that are in the same price range?

Gas block - I am guessing that I should do an adjustable gas block since I have plans for a suppressor in the future. Is there one I should be looking at? the Barrel has a 0.750" gas port.

Trigger - geissele s3g, sd3g, hyperfire 24 3g, or 24c

Lower build kit - one without a trigger preferably.

Any other odds and ends that I am not thinking about?

Thank you for all of your input!

parttimer · Nov 30, 2015

I almost forgot the buffer. I was looking at the spikes T2 or t3.
Is there a prefered buffer spring?

Thank you

amoebicmagician · Nov 30, 2015

good choice on the barrel! Melonited and from a good manufacturer

parttimer · Nov 30, 2015

Thank you. Hopefully the I can get some good advise on more quality parts that won't break the bank

BradMacc82 · Nov 30, 2015

BCG, not aware of any one specific brand that truly holds an edge over another as far as the x39 goes. MGI sells the bolt head and extended firing pin in a package, so don't drive yourself crazy trying to find a dedicated x39 BCG. You can use a standard 5.56 carrier and swap the bolt head.

Gas block, SLR and Syrac are good choices. The gen II variants from both brands are on the same footing as far as I can comment, in regards to ease of use and install/cleaning. Both are pre-dimpled for pinning, so that's a nice bonus. #31 Carbide drill bit will be needed to pin either.

Hand guards, completely your choice there.

LPK's can be had without the FCG - JoeBob's comes to mind, and KeepShooting.

FCG, I'm biased - Geissele or nothing. The SD3G makes for a hell of a fun rifle.

Buffer - start with standard carbine buffer, with the adjustable gas, it's not worth the juice to spend for the Spike's buffers.

parttimer · Nov 30, 2015

Thanks for the input Brad.

I guess on the hand guard I am wondering if I should why away from the 15" rail due to the adjustable gas block. I am also not sure on m-lok or key mod

I am looking to buy once and cry once

BradMacc82 · Nov 30, 2015

Carbine length gas on that barrel, 15" rail may be too long.

SLR and Syrac include an extended length hex key for doing adjustments to the gas block, but I think you'd want to keep the rail under 13" so you can make adjustments w/out having to pull the rail off.

Boss94 · Nov 30, 2015

You need a Redxarms firing pin !!!

dontpanic · Nov 30, 2015

If your lower is not preban, you need a HBAR. The one you listed is not.

Yes, Colt made a 7.62x39 AR-15. So it is banned, unless it is a HBAR.

Wishing it was not, does not make it legal.

parttimer · Nov 30, 2015

dontpanic said:
If your lower is not preban, you need a HBAR. The one you listed is not.

Yes, Colt made a 7.62x39 AR-15. So it is banned, unless it is a HBAR.

Wishing it was not, does not make it legal.

I was under the impression that all .30 cal rifles were considered to be h-bar am I mistaken?
If I am I will just use a pre ban lower I have in the safe.
I really hate how stupid this pre/post ban law is.

parttimer · Nov 30, 2015

Boss94 said:
You need a Redxarms firing pin !!!

Noted and thank you

dontpanic · Dec 1, 2015

parttimer said:
I was under the impression that all .30 cal rifles were considered to be h-bar am I mistaken?
If I am I will just use a pre ban lower I have in the safe.
I really hate how stupid this pre/post ban law is.

A lot of people want to think this is true. Unfortunately, using the HBAR guidelines for .223/5.56, it should be marked or advertised as a HBAR.

These laws suck. But we are stuck with them. For now.

parttimer · Dec 1, 2015

I will check the barrel for any H-bar markings when I get home from work.

Thank you for your input

Bigrascal · Dec 1, 2015

I had an issue with light strikes on Tula and Wolf ammo with two different lowers.
The lowers were off my everyday shooters and never had an issue while shooting 556.
Knowing this when I built the 7.62 lower, I installed a Heavy Hammer Spring... problem all fixed.
I also used the Spikes T2 buffer

amoebicmagician · Dec 1, 2015

i have found it's not so much the hammer spring that is the problem, the firing pin needs to protrude a bit more to reliably ignite berdan primers. You can relieve the firing pin yourself, or just buy one with your bolt head, they aren't expensive.

My experience with melonited/nitrided barrels is that they fire bimetal jacketed rounds AMAZINGLY well. Not quite sure why, but once the barrel is fouled with a couple fifty rounds through it, the accuracy really settles in to something awesome. Even with wolf you can get some damn fine results. Not sure if this is because wolf is being made by barnaul now, but I've really had some exceptional results from them out of nitrided AR and AK barrels.

I had originally thought that 7.62x39 out of an AR would necessitate a heavier buffer, but have found if the gas port is in spec, a carbine buffer works just fine.

Ifdot · Dec 1, 2015

BCG - is there a certain brand that is really where its at? I know I will need and extended firing pin to run steel cased ammo which is what I will feed it most often.
Get one with an mpi bolt and extended firing pin, inspect the staking and gas key bolts properly torqued

Hand guard - I was looking at the Midwest industries SSK 15" . It is a free float one piece lightweight rail key mod system. Should I be looking at a m-lok rail? Will a 15" rail create problems for an adjustable gas block? Are there any other lightweight rails that I should be looking at that are in the same price range?
I too have been eyeing this rail, and from what I've been reading m-lok is the way to go now. The 15" won't be an issue if you get the extended hex key for adjustment. The SLR extended is @$8

Gas block - I am guessing that I should do an adjustable gas block since I have plans for a suppressor in the future. Is there one I should be looking at? the Barrel has a 0.750" gas port.
SLR set screw type. Best deal I have found on them is http://www.righttobear.com/SLR-Rifleworks-Sentry-7-Set-Screw-Adjustable-Gas-B-p/sa7-sm.htm
SLR has crazy shipping prices fyi

Trigger - geissele s3g, sd3g, hyperfire 24 3g, or 24c
Geissele

Lower build kit - one without a trigger preferably.
They are all basically the same. Engage sells one that has a nice soft rubbery ergo grip I enjoy.

Any other odds and ends that I am not thinking about?
Go with a Tubbs spring and generic carbine buffer. You can always add weight to the buffer if needed.

parttimer · Jul 27, 2017

Ok it's time to bump this old thread. I put this project to the side a while ago to make some other purchases. No it is time to get back to it.
My wife wants to take me to gun shot tomorrow and wants to drop a couple bucks on me. It's time to pick up some parts.

In addition to the parts on the op I now have a slr adjustable gas block, s3g trigger, a buffer tube setup, and a lower parts kit.
I still need a bcg, a handrail, an upper parts kit.
The Midwest handrail mount will not work with my billet upper without some work with a file to do some fitting work. I may still go with it or do another lightweight 15" rail like the oden works 02 light but I don't know anything about these rails.
Bcg- any must haves for one of these? Based on the writings of Clandestine I will avoid nickel boron. Any suggestions on things to look for?
Optics- I have a bushnell 1-4 at optics but the BDC is for .556. I am looking at the primary arms 1-6 with 7.62x39 BDC. Does anyone have an opinion on this scope?
Also is there anything I have missed on my list other than a generic upper parts kit?

TheGunnyRet · Jul 29, 2017

Check Out ORION Guns in PA, They're online to, I got mine from them with SS HBAR...runs great...only issue I have is Magazines. The Solution is the feed side of the mags need to be gut down to better feed the ammo.

And yes you need to have a HBAR in MD.

Sirex · Jul 29, 2017

Fearing a Hillary victory last year, I ran out and bought a budget Bear Creek Arsenal 7.62x39 rifle. So far, I have been happy with the rifle itself. Mine has been pretty darn accurate, especially with cheap crappy steel case ammo. My upper had no iron sights though, and the barrel was parkerized, so I just ordered this upper last week since it's on sale. Nitrided barrel, and a A2 sight. I guess my goal is to make it look just like my 6721. But, aside from some mags issues (CPD), the rifle has been great despite the low cost.
Upper; https://www.bearcreekarsenal.com/up...nd-guard-w-front-sight-ua762chb16110-m-shg-fs

Sticky · Jul 29, 2017

I have two x39 AR's, one rifle, one pistol. Both use extended firing pins, one has a Sota Arms bolt, the other a bolt from Lehigh Defense, both have been fine, but I do have a spare Sota just in case (they have to thin the bolt to accommodate the larger case diameter, so they are slightly weaker than a stock AR bolt in that regard).

I use SLR gas blocks and with the extended allen wrench, you can reach way down under a rail, no issues.

Help me build my new 7.62 x 39 Ar

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