My First AR-15 Upper Build

A first timer's experiences assembling an AR-15 upper receiver.

Written by rtfjr86
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It took me about 5 months to save up the cash to purchase all of my upper receiver parts as I am a father of 3 on a budget. However, the time has come to assemble my upper. The part that goes bang! I’m really excited to get it done and finally have my first (and hopefully not last)  AR-15. You can check out my experiences assembling the lower receiver here: AR-15 Lower Receiver. With that said, let’s get to it.

Parts List

  • Aero Precision AR15 FDE stripped upper receiver - $95
  • Aero Precision AR15 upper parts kit - $20
  • Aero Precision ambidextrous charging handle - $68
  • Aero Precision low profile gas block - $21
  • Aero Precision 5.56 black nitride bolt carrier group - $135
  • Aero Precision mid length melonite gas tube - $17
  • Aero Precision 16" .223 Wylde fluted stainless steel barrel - $216
  • Aero Precision 15" ATLAS R-ONE hand guard - $168
  • Kaw Valley Precision .223/5.56 linear comp FDE cerakote - $46

Some of the Parts For My Upper Build

The Build

As a guide, I followed the assembly instructions posted over at Pew Pew Tactical. You can view that post here.

Following the above mentioned tutorial, I began with the forward assist and the dust cover. The forward assist was fairly easy to install. I started the pin with a brass hammer and finished it off with a punch. There was one thing that kind of caught me off guard. Once the forward assist pin is started, you have to press in the forward assist while you push the pin in the rest of the way. Otherwise, your forward assist won't move. I had to back out the pin and make a second attempt while holding the button, which was pretty easy. I think the dust cover was literally the easiest part to install on the whole build, including the lower receiver.


Stripped upper receiver with the dust cover and forward assist installed


Next, I installed the barrel. Luckily it is idiot proof as the barrel is notched to line up with the upper receiver. Next, I put a little anti-seize on the barrel nut threads and screwed on the barrel nut. I don’t think my particular barrel nut needed to be lined up with the gas port, but I ended up using one shim anyway to make it line up as best as I could. Next torqued down the barrel nut to about 40 ft/lbs. A quick note on this. This is where having a really good vice would have been a huge help. My vice is just a cheapo, clamp on vice from Home Depot. It works well for light work, but anything else requires something more durable. I essentially had to hold the receiver block in the vice while torquing the barrel nut at the same time. An unnecessary pain in the butt.

I then moved on to pinning the gas tube to the gas block. The difficulty here is getting enough leverage on the pin without scuffing up the nitride finish. I wrapped an old rag around the gas block, set in on the concrete outside, and used a punch to drive the pin in. It was then time to install the gas block on the barrel. I read that some folks leave a small gap between the gas block and the shoulder of the barrel for optimal gas port alignment. I also read that most gas ports are larger than those on the barrel to accommodate imperfect alignment. With that in mind, I pushed my gas block all the way against the shoulder and hand tightened it as tight as I could without stripping the screws.


Gas block


Barrel and gas tube


From there, I installed the muzzle device. Before I installed it, I used a little bit of anti-seize on the barrel threads. Because it is a linear comp, it does not have to be timed. However, because I’m a perfectionist, it bothered me that the wrench flats weren’t lined up. So, I ordered an FDE cerakote crush washer to match. Now the wrench flats are at the three and nine o’clock positions. Next time I need an FDE crush washer though, I think I’ll just spray paint a black one and call it a day. Torquing the muzzle device was a bit of a pain, again because of my cheap vice. The plastic receiver block just kept slipping out of the vice. As you can see, I skuffed up the cerakote installing the muzzle device. I doesn't really matter to me because onece I start training with the rifle, it is going to get a lot scars anyway.


Muzzle device and crush washer


Linear compensator from the front


Wrapping up, I installed the hand guard and the Magpul sights as far forward and back as they could go. Super easy. Nothing of note to report. I installed my BCM vertical foregrip with ease. MLOK is a foolproof attachment system. I angled mine forward because I plan on using it more as an index and a hand stop for a modified c-clamp grip (see Lucas Botkin at T-Rex Arms). I put in the charging handle and the bolt carrier group and voilà, I have assembled my first upper receiver.


Rear sight


Front sight and hand guard


I’m super pumped. I actually have a fully assembled AR-15. I’m excited to get it to the range and test it. Will it explode? Does it cycle properly? Will I be able to properly zero it? I can’t wait to find out. I'm quite happy with the results though. I got exactly what I wanted from the start, rather than purchasing a generic rifle then tearing it apart to make it my own. Also, I'm glad that I have a much better understanding of how the AR-15 platform functions. Next on my purchase list is an optic, a weapon light, and a sling. Oh yeah, and a cabinet or safe to store my new rifle in!


The completed upper


The complete rifle on a stand


The complete rifle

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