AR-47 Rifle Build

I mentioned on the boom stick thread that I was building my first AR, and there seemed to be some interest in a build thread, so here it is. Mods, if you feel that this is not appropriate please remove.  Also let's please keep any political discussion out of this thread.

I have been shooting for decades and had been interested in assembling an AR for several years. The pandemic seemed like a good time to give it a try, but I obviously was not the only person with this idea, as many parts and ammo are on back order or are expensive and hard to find. In particular the standard AR caliber of 5.56x45 is sold out almost everywhere. Because of this I decided to do a build chambered in 7.62x39. This is the same round used by the AK-47 and other Eastern Bloc rifles. This ammo is still relatively cheap and plentiful, and it is a sibling to the rounds used in my WWII Mosin Nagant, which was my first rifle. 

Here are all the parts used for the build:

Parts list is as follows:

• Aero Precision stripped lower (this is the legal "registered" firearm)
• Palmetto State Armory Lower Parts Kit with Magpul MOE grip and stock in olive green (for that eastern bloc feel)
• Magpul M-lok AFG forward grip, also in green
• Bear Creek Armory 7.62x39 side charging complete upper. When I ordered this I didn't realize it used a side charging handle, rather than the standard AR platform rear charger, but I decided it was a nod to the AK and went with it.
• Cheap Amazon Special Reflex site. This is the only foreign made part on the gun, and I will probably replace it with something better in the future

For the build I followed this guide from Pew pew tactical. Assembly took about an hour, including taking photos and helping my daugther with homework.

First up was the magizne release and trigger guard. A brass punch was very handy for driving in the roll pins without marring the finish.

Next up was the bolt lock and it's spring. The lower reciever was protected with tape and the roll pin was started.

Once the roll pin was in place the spring and detent were installed in their hole and the bolt release button was slotted in, then the roll pin was driven home. This was probably the most difficult part of the build. One slip and the finish could be scratched or the ear broken off. The brass punch and a soft hammer did the job.

The trigger assembly and hammer were next. The appropriate springs were installed on the hammer and trigger and the disconnector installed onto the trigger.

Next the trigger and disconnector were installed into the lower, followed by the hammer. The pins are the same and can be installed in either direction without issue. 

A few manual cocks of the hammer, and pulls of the trigger (making sure to stop the hammer from smacking into its stop) confirmed it was working as it should.

Next on the list was the safety lever and it's detent and spring, as well as the grip that holds the spring in place. The hammer was cocked to make room for the safety lever, the safety was inserted in the "fire" position and the detent was dropped into its hole in the lower under the grip. The spring went into its hole in the top of the grip and the two pieces were shoved and screwed together. Now it's starting to look like something!

The buffer tube and rear take down pin were next. This is a semi-complicated order of assembly. The castle nut on the buffer tube needs to be screwed all the way to the back, and the end plate installed onto the tube. then the shorter of the take down pins is installed, then the detent and it's spring are dropped down the small hole on the rear of the lower. Next the buffer tube and end plate was carefully screwed on a few turns. With it partially screwed in the buffer retainer and spring are installed into their hole in the female threads of the lower, and the buffer tube screwed in until it just contacts the retainer, all the while being careful not to drop or bend the take down pin spring. once the tube reaches the retainer the retainer is depressed and the buffer tube screwed in one more turn until it is vertical and holds the retainer in place. Finally the end cap is pushed forward retaining the take down pin spring and the castle nut hand tightened for now.  Whew!

The front take down pin was next. This can be a pain and if you are not careful the spring and detent will launch themselves across the room, never to be found again. My kit came with an extra spring and detent for this very reason. A 1/4" Clevis pin can be used as an installation tool to stop the spring from launching. The clevis pin is inserted from the opposite side of the takedown pin and the hole closest to the end is aligned with the hole for the takedown spring and detent. The spring, then the detent are dropped through the clevis into the lower, then compressed with a small punch or allen wrench. The clevis is then rotated to trap the spring and detent in a compressed position. The takedown pin is installed pushing the clevis out of the lower while keeping the spring trapped until it pops up into the slot in the takedown pin.

To wrap up assembly the castle nut is torqued to 40 ft-lbs using an armorer's wrench. I protected the buffer tube with tape so it didn't get scratched.

The nut should be staked in place using a punch to deform a the edge of the end cap into the the provided notch on the castle nut. I skipped this for now as I may want to install a different end plate that allows a sling to be mounted.

And with that the lower is done!

Completing the build was as simple as attaching the upper to the lower using the take down pins, and mounting the forward grip and optics onto the upper.

You can also assemble your own upper, but it is a bit more technical and requires some specialized tools and "go/no-go" chamber gauges to make sure that the head space is correct. When I bought my lower reciever the gun store was having a twofer sale, so I also bought an AR-10 lower.  I plan to assemble the upper for that rifle myself.

Here is the finished rifle with a 30-round magazine. The magazines for 7.62 chambered ARs are different than a standard AR and have a more pronounced banana shape due to the taper of the rounds.

It was a fun build, and I look forward to testing it out!

Looks like a total... blast.

That is seriously badass. Thank you for posting the how-to...

Mind sharing the total cost for everything? I'm definitely interested building something similar. Thanks!

lnlogauge said:

Mind sharing the total cost for everything? I'm definitely interested building something similar. Thanks!

Yes, I would also be interested in knowing this as I would like to build one as well.

Ive been curious how the AR platform eats 7.62x39. If it likes the "cheap" steel case chi-com stuff, then awesome. If you have to buy brass case, not so awesome.  Curious about accuracy as well. 
 

nice build!
 

i lol'd at Pew Pew Tactical

Awesome - cool build. I too am interested how the AR platform digests commie rounds.

The build cost me about $750.

The 7.62 ARs sometimes have issues feeding. Feed issues are usually caused by the magazine, the C products Dura Mags are supposed to be reliable. I have 2 of their 20 round mags, and 2 30 round AR Stoner mags from Midway USA.

Another issue that can happen with steel case ammo is light primer strikes. You can buy an Enhanced firing pin for a bit over $10 that seems to solve the issue. A mil-spec firing pin can also be modified by taking a thousand or two off of the inside of the lip on the back of the pin, allowing it to protrude a bit farther out of the bolt.

I have 80 rounds of steel case ammo that I am going to run through it today. I'll post how it goes.

I dig it!

Roll pin punches make life much easier if you're going to build many more of these.

Headspace on an AR is set when the barrel extension is installed.  Most folks don't buy the barrel and extension separate. As long as the barrel extension and bolt are in spec headspace isn't going to be an issue.

If the barrel and bolt are from the same manufacturer I wouldn't sweat it. 

If it chambers a round and goes bang, look your brass over for abnormalities, if it looks normal, all is well.

Go No Go gauges aren't a bad tool to have, and by all means use them if it makes you more comfortable, but there are thousands of home builds in the wild mag dumping every chance they get, who's builders don't even know what headspace is.

In reply to bigdaddylee82 :

Thanks for the tip!

I got out before work and tried it out.

The good news is that it shoots..... sometimes. I was having a big issue with light primer strikes. I also had a few feed issues, but that may have been due to having to hand charge every other shot. After 80 rounds here are all of the ones that didn't go off:

I've ordered an enhanced firing pin, and will probably try to modify the one I have. The cheap sight was way off, I couldn't get it on the paper at 20 yards. I moved in to 10 yards and it was way right and low. I got it dialed in at 10 before heading home. 

I also got a chance to exercise the suspension on the Land Cruiser.

Light primer strikes...  You need to remove, disassemble, lube and inspect your bolt. 

If you want a better trigger, shoot me an e mail.  I have several left over from my builds and spare parts.  I will send you an ALG mil spec trigger.  It's only worth $25 or so, but it is a huge improvement.  I use Gieselle triggers, but that is a slippery slope you may not want to hop on.

Also if you build another get an M4E1 lower from Aero.  It has a few enhancements that I really like such as the threaded steel pin with 0.050" hex head for the bolt catch.  It also has a threaded 0.050" hex screw to retain the selector switch detent and spring. 

I assembled another 5.56 build from parts last night from memory this time. 

Uppers are easy to assemble too. 

I've always liked C products magazines for ARs.  I'm a big fan of steel mags.  My first plastic mags came apart in the TX heat and unloaded themselves.  I still have a few polymer mags, but I'm not a huge fan in spite of all of the favorable press. 

I also have a 7.62 AR, but it's 7.62x51 aka 308 not 7.62x39 like yours.  For an ammo availability and cost standpoint, I have always been interested in 7.62x39, but I already have 3 rifle calibers.  I do not need a 4th. 

In reply to bgkast (Forum Supporter) :

Looks like a great day before work, even if you had a bunch of light strikes. Are those rounds just trash now or can you run them through again for a second hit?

The nickel/boron two stage trigger from Palmetto is one of my current favorites, but I've also heard of people hating it.

In reply to AnthonyGS (Forum Supporter) :

I disassembled and lubed the bolt and firing pin before firing it. I will do it again and try shaving down the pin stop a bit, then try running the light strike rounds through it again. I wanted an M4E1 lower, but they were sold out. I got an M5 lower that has those features, and am slowly collecting parts for a 7.62x51/.308 build.  I'll shoot you an email about that trigger!

While cleaning the rifle this evening I gave modifying the firing pin a try. A lathe would be the proper tool, but I made due with a drill press and file.

I took off 10 thousands

Hopefully that does the trick.

General AR question. With the gas charge cycling, I would imagine the gas tube gets pretty grungy. Is there a method to clean it? Am I overthinking it?

barefootskater said:

General AR question. With the gas charge cycling, I would imagine the gas tube gets pretty grungy. Is there a method to clean it? Am I overthinking it?

You can buy long pipe cleaners from Brownells or Midway sold as gas tube cleaners, but most folks consider gas tubes to be self cleaning.  There's a lot of pressure, velocity, and heat, in that tiny smooth wall tube.  Unless you're shooting a lot of .22 LR out of a drop-in conversion, there's little concern for gas tube cleaning.

If I was really concerned, I'd be more likely to keep a spare $10 gas tube around, than a $10 bag of long pipe cleaners.

bigdaddylee82 said:

barefootskater said:

General AR question. With the gas charge cycling, I would imagine the gas tube gets pretty grungy. Is there a method to clean it? Am I overthinking it?

... Unless you're shooting a lot of .22 LR out of a drop-in conversion, there's little concern for gas tube cleaning...

 

Ahhh, that explains the abysmal state of a gas tube I recently replaced out of one of my 16 in uppers. That particular upper had seen thousands upon thousands of .22lr rounds shot through it out of a CMMG conversion and was in a state of carbonized filth - reminiscent of a early direct injected engine intake valve.