7.62×39 AR-15 Build

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My 7.62×39 AR build

 

Believing the 7.62×39 could be a very accurate round, I wanted to undertake my own custom build. I felt the platform would be very important, and that it had to be gas impingement, and not a piston system. Why? It’s too difficult, if not impossible to free float the barrel of a piston design. Arguably, free-floating is something you’d want to do to an already accurate rifle, to fine-tune and eek-out every last bit of accuracy. Free floated AR barrels are very common nowadays, not to improve accuracy, but because… anyone? Because they look tacticool, and people can hang all kinds of neat stuff on them! Lights, bipods, vertical grips, hand stops, angled grips, lasers, backup sights, angled sights, QD swivels, red dots, scopes, magnifiers, and anything to be as pretend combat creative as one can be. You’ve seen those funny pics!

 

7.62×39 AR bolt from AR15Performance

My first goal was a search to seek out anyone that had improved the durability of the AR bolt. I had even thought about designing one, along with a matching barrel extension. Then I ran across AR15Performance. They are the only ones that I could find that have gone beyond stronger steels and other attempts to reduce bolt wall/lug fracturing.

 

 

Reamed for 7.62×39 case. Note wall thickness.

The traditional method in making the 7.62×39 case work is simply to ream out the bolt face to fit. In all cases with this method, you compromise the structural integrity of the bolt by removing that much material. The AR15Performance bolt is a redesign that is claimed to be 35% stronger than any bolt on the market. Any Caveats? Yes. From them, you can only get the bolt and extension in conjunction with ordering one of their 7.62×39 barrels, where they will install the extension and headspace the bolt before shipping. Their barrel is a mid-length gas system, so the cost of the combination with a mid-length gas tube, was $300 shipped. Not included is a firing pin, nor cotter pin.

Standard AR-15 bolt

The bolt is ground slightly at the rear to allow for more firing pin tip protrusion. I measured .003″, so not much. And maybe not enough. I decided to order an “enhanced” firing pin, which is slightly longer. Besides, I’d rather modify the $10 pin as opposed to screwing up that bolt!

 

11 degree target crown

The barrel is excellent.
Nice machine work, a full 11 degree target crown, and Melonited. The barrel extension and feed ramps also appear to be well thought out.

 

 

 

 

 

As always, I faced the upper receiver to ensure it would be square to the bore, along with some fine tweaking to align the cogs for the gas tube. The barrel nut was torqued to 60 ft.lbs.

 

The rest of the upper are from parts I had from other builds, starting with a narrow (1.5″ OD), lightweight MI M-Lock 13.5″ handguard and barrel nut, Diamondback upper receiver and bolt carrier, and a basic charging handle.

12.6″ handguard from Midwest Industries (MI-G3M12). 9.4 oz with barrel nut. M-Lock. QD points.

 

BCM Gunfighter Grip, Mod 3.

I made another change to this build by adding a BCM Mod 3 grip, which is more vertical, and feels more natural to me. I did not install a muzzle device, other than a thread protector, since I want to perform accuracy testing first. The lower contains a basic build kit (including trigger) on a Boberg billet receiver. The stock is a Magpul CTR.  This combination, without magazine and without sights or scope, weighed in at 6 lbs even. My scope and mount will add another 20 oz. I didn’t put this together as a lightweight build, and could save weight with a lighter buttstock and some titanium parts, but I’m not going to go too crazy with that. Famous last words?

 

 

 

 

Trijicon Accupower 1-4×24 with Aero Precision mount. Total weight with mount and lens caps 20 oz.

I mounted a Trijicon Accupower 1-4x scope, and with a couple of C Products 10 round 7.62×39 magazines in hand, I headed to the range. The ammo I took was Hornady SST, Silver Bear, and Golden Tiger. I’ll be shooting with a bipod and rear sand bag.

 

At The range. Spoiler alert…the Golden Tiger would not ignite at all. Their primers are recessed, and even though the strikes appeared to be solid, it just wasn’t enough to light it up. The Silver Bear had two light strikes, and the Hornady was 100%. I definitely need to install that “enhanced” firing pin. I’ll wait to see the results before thinking about a heavier hammer spring. It makes me wonder if my ‘fancy’ drop-in trigger will work. It’s a Wilson Combat TTU which currently resides in my Sig MCX. Please just be the firing pin! 😕

 

The distance was 50 yards for function and reliability testing, along with sighting in the scope and general accuracy checks. I was pleased. Here’s the adjustment target using 123 grain Silver Bear. I numbered the hits to show the order of the adjustments. No complaints here and was a little surprised that these first 10 shots followed the scope adjustments so well.

 

And, BTW, throughout the entire test, using a couple of 10-round C Products magazines, there were no magazine related failures, and no extraction nor ejection issues. I have a couple 30 round C Products mags that I will try during the next range outing. I normally don’t use large capacity magazines at the 100 meter indoor range because of clearance issues on the bench. But, I do use them while standing or propped on my elbows. Have I mentioned how much heavier a 30-round 7.62×39 magazine makes the rifle?  Ugh, and hence the popularity of the 5.56?

 

Silver Bear 123 GR
Hornady SST 123 GR

Here are a couple more on a 1.5″ circle at 50 meters. No flyers, so once again, very pleased. I will use the Hornady for hunting, although the Russian stuff doesn’t appear to be too shabby! And no scope adjustments were required between ammo types. Then again, this is only 50 meters so we’ll see how it does at 100 meters on the next outing.

 

 

 

 

 

The Boberg lower receiver. Nicely machined, but way over priced, and now they’re out of business.

 

C Products 30-round 7.62×39 magazine

As this is my first AR 7.62×39, I wasn’t sure which magazines would work the best. Reading reviews and opinions, it’s as bad as the ‘which caliber’ arguments. LOL. I decided to start off with the C Products 10 round magazines for bench shooting (or hunting), and a couple C Products 30 round magazines just because those danged Zombies could be right around the corner. So far, I’ve had zero failures with the 10 rounders. The other magazine I was considering was the ASC, but glad I chose the C Products for now. 

 

 

I changed the trigger group from the Wilson Combat TTU to the Velocity 4lb Trigger. This is the model designed for harder hammer strikes to light up steel cased ammo. It is a true and consistent 4lb single stage trigger with no takeup, no creep, and unnoticeable over-travel. The reset it very short, and there’s no play once the trigger is ‘set’. It’s very similar to the feel of the Wilson Combat single stage TTU. A trigger pull gauge shows a consistent breaking point at 4lbs exactly each and every time. I’m not sure triggers can get any better than this, especially when design with such a hard hammer strike, and so far, not a single light strike with a variety of Russian ammo.

 

I also added the AR 7.62×39 Enhanced Firing Pin from Black Rifle Arms for a bit more reassurance. So far, it’s been perfect. 

 

I haven’t tried it yet, but I ended up with a titanium spiral radial ported brake. My understanding is that having holes all around improves the way gases push ahead of the bullet more evenly with less turbulence. Hype? I’ll find out. Using a simple thread protector is one way to ensure the muzzle device isn’t interfering with accuracy. Plus, a Linear device or thread protector will allow fellow bench shooters a little more peace by not sending ‘shock waves’ in their direction!

5/8 x 24 Thread Protector. V Seven Weapon Systems.

 

 

 

 

 

 

 

 

 

 

 

 

 

Lightweight (claim is under 6 oz) Mission First Tactical Battlelink stock. When it arrived…to the scales. Weighs in at 6.4 oz without the included QD sling attachment. Lies seems prevalent among this industry. Still a nice stock, though, and feels good on the shoulder. I have two of these, and both had a problem with the adjustment pin coming loose and falling out. Fortunately, I was able to recover my pins and add some LocTite in hopes it won’t come loose again. The engineering’s not bad, but the execution really sucks when it comes to ensuring the pins don’t disappear at the range or elsewhere. Plus, this stock is not all that tight fitting and rattles and moves around too much for the discriminating builder. Just goes to show that saving a few ounces here and there may not be such a smart move. Fortunately, they’re not very expensive and can be tossed when the next greatest lightweight stock hits the market. 

 

Matrix side charging upper receiver.

 

This is what all AR platforms should be! The old charging handle had its day, however impractical it may have been, but the side-charging design makes way too much sense to ignore. They’re a bit pricey, but worth it to me. The Matrix design is the only side charging upper I know of that doesn’t need any bolt carrier modification or a custom cam pin. And nothing protrudes out of the upper. Great!

 

 

TPI Titanium Full Port Muzzle Brake

MFT Battlelink Minimalist Stock