Build a Complete AR-15 Upper in Under 45 Minutes

All the parts you need to build a complete AR upper! Parts and pricing are listed below.

As we stare down the barrel (no pun intended) of another potential gun grab/ban, I felt like it was time we take a look at exactly how to keep your AR running indefinitely.

One thing we learned from the 1994 ban, the components like magazines and lowers will last pretty much forever. In fact, there are very few things on an AR that actually wear out. That said, there are some critical parts that may need to be replaced.  Today we are taking a look at those.  And as a bonus, I’m going to show you how to build an entirely new upper in under 45 minutes.

The Barrel

For this new upper assembly, I’m using an ULTRAlight 16.1-inch barrel.

First off, the barrel. Most people won’t shoot out an AR barrel in a lifetime, but if you shoot a lot, be prepared for this one. The life of the barrel depends on a lot of things such as coating, materials, and how fast you shoot.

The 10.5-inch barrels we used in the Army usually lasted between 10,000 and 12,000 rounds. I have had melonite-lined barrels that lasted 45,000 rounds before they shot out. A pretty good judge is 10-20,000 rounds. The nice thing is, your gun will still fire if the barrel is shot out. You just might not be able to hit anything.

Fortunately, barrel replacement on an AR-15 is one of the easiest tasks there is to do. ARs are like LEGO sets, no real skill required to swap parts. The only thing you might need is an armorer’s wrench, depending on the barrel nut. There are tools that make this process easier, but that is the only one required.

***Visit ODIN Works for Some Great Deals on AR Parts! ***

The Bolt

Second is a bolt, with an even sketchier life cycle. I have seen them shear lugs around 10,000 rounds and others go 85,000-plus rounds. It is the most common breakage on an AR but still doesn’t happen often. You can score a new bolt for about $40, or an entire bolt carrier group for about $100.


Swapping is easy!

Learning to swap a barrel is also a great skill to have, for a variety of reasons. In the current AR panic, you may end up with a cheaper gun. The nice thing is, as long as the upper is built to spec, you can replace everything else.

The difference between a 4 MOA gun and a .5 MOA gun is pretty much all barrel and barrel nut. As you save up your pennies, you can slowly turn a bargain-bin special into the meanest gat on the block. This is also how you change calibers, one of the best benefits of having a modern sporting rifle. With a base lower, you can easily build uppers in .300 AAC Blackout, 224 Valkyrie, and a variety of other calibers.

Building the Upper

To demonstrate how to swap a barrel, I opted to just build an entirely new upper. A shopping trip to ODIN Works, native to Boise, yielded all the parts I needed (see below).

The finished product. Was able to shoot .75 MOA in high wind.

The point of the exercise isn’t to show you how cool I am with the build skills, in fact just the opposite. I suck as a gunsmith, I make a much better gorilla in a suit. People built my guns for me pretty much until I started to work at GunsAmerica. The only thing I am certified to work on is a Glock, and that is mostly because the armorer’s kit consists of one punch and a razor knife.

If I can do it, you can do it. I also built mine without using any special tools because I also don’t care about scratches. Using just a hammer, one punch, needle nose pliers, and a crescent wrench, I slapped together a .75 MOA upper in about 45 minutes. This isn’t like a 1911 with all manner of hand-fitted parts.

If you are looking for new parts or a completely new upper, ODIN Works is a one-stop shop. These are the parts I used in my new ULTRAlite upper receiver.

Parts and Pricing

223 Wylde ULTRAlite 16.1″ Mid Length Barrel. Price: $290.00

AR15 XCH Charging Handle. Price: $45.

FDE O2 Lite KMod Forend – 15.5-inches. Price: $230.00.

Mid Length Gas Tube.
Price: $12.00.

223 Black Nitride Bolt Carrier Group. Price: $129.00.

FDE Billet Upper Receiver-AR15. Price: $179.00.

Adjustable Low Profile Gas Block. Price: $89.00

ATLAS Compensator.
Price: $99.00.

Don’t want to build your own upper?  No worries.  You can always:

***Shop GunsAmerica for a New AR***

About the author: Clay Martin is a former Marine and Green Beret, retiring out of 3rd Special Forces Group. He is a multi-decade and -service sniper, as well as 3-Gun competitor and Master ranked shooter in USPSA Production. In addition to writing about guns, he is the author of “Last Son of The War God,” a novel about shooting people that deserve it. You can also follow him on twitter, @offthe_res or his website,

{ 10 comments… add one }
  • BJ October 2, 2019, 10:28 pm

    Interesting how you were able to build an AR15 upper without a barrel nut. Very impressive. Thank you for showing all the needed parts!

  • Russell Fayer March 14, 2018, 12:55 pm

    Excellent video, I like your style. I’ve checked out Odin Works.
    Where did you get the barrel nut and the piece it goes into to hold the handguard?

  • FirstStateMark March 9, 2018, 12:08 pm

    Thanks Martin. You made that look easy to someone who wouldn’t have tried that before watching the video.

  • Randall March 9, 2018, 11:24 am

    My brother you definitely more geared for a sledgehammer and a two handed sword.

  • jgw March 9, 2018, 10:16 am

    One of the main problems I’ve had upgrading firearms modular like an AR15 is accumulating lots of spare parts. Thats how I’ve wound up with 6 complete rifles. Too tempting to build up another one when your already a majority of the way there spare parts wise. When you get start getting bored with yet “another” 5.56 start considering adding other calibers to your arsenal. I love my 300blk and .22 dedicated setups.

  • MattD March 9, 2018, 9:45 am

    Mr. Martin,
    The video is an excellent example of what you can do to assemble/repair an AR under a stressful situation.
    The shooting example was certainly proof that that particular rifle will shoot very good groups, safely, without a malfunction.
    A thought is because you used all ODIN Works parts, things had the best chance to fit well.
    I’ve only assembled one and a half AR Uppers, one was a CCMG .22 LR bolt conversion and barrel ergo the 1/2 designation, and the other was a WYLDE barrel build with both being based on Aero Precision upper components.
    I could go into the parts/assembly research I did and tools I purchased to try and ensure they were safe to shoot but I’d rather point out that under normal circumstances, I suggest considering either to use recommended tools and assembly procedures and/or minimally have a gunsmith check the build including doing a headspace check.
    I bought the Pacific Tool and Gauges headspace gauges and it gave me a world of confidence in the WYLDE barrel after they fit, prior to assembling the barrel, per the Go/No Go/Field gauge instructions using a, removed, stripped bolt face, the correct way to check headspace.
    I have 3, BCGs and will check headspace using the stripped bolt face from each of those in each barrel I plan to use them in, before taking them to the range.
    I do appreciate the Odin parts evaluation and will certainly look into their parts for future builds.
    I did use a Seekins adjustable gas block on the WYLDE build, set it for 100% lock back cycling using the minimum pressure .223 Rem load with a 55 gr FMJ bullet using both IMR 3031 and RamShot TAC reloads expecting it to work with any higher pressure, similar loads as well and so far it has.
    The idea was to reduce the wear on the moving parts by using the adjustable gas block to run the BCG 100% using minimum bleed off pressure to accomplish that.
    The tradeoff is lower reliability after the action gets dirty, not a factor for me.
    Again, I appreciate your proving what can be done but would like to warn people that parts tolerance stacking can cause problems.
    With regard,

  • Kb31416 March 9, 2018, 7:34 am

    Amen to the author and the previous poster. The AR platform is amazingly versatile and LEGO set simple to build and work on.
    My latest personal interest is working on new wildcat cartridges for the AR15. 300 AAC is just the tip of the iceberg in capability. In two broad categories, 223 based an other parent cases, a short list:
    223 based:
    300 AAC, 7.62×40 WT, 277 WLV, 357 AR
    Other parent cases and not wildcat:
    22 Nosler, 22 Valkyrie, 6.8 SPC, 7.62×39, 5.45×39, 6.5 Grendel, and many more.
    There are also 44s in the works, and many more. If anyone is looking for a new excuse to build more rifles and optimize theirs for deer or hog hunting, or anything else, investigate Modern Sporting Rifle Evolution. Much fun, but it has made it impossible for me to keep my New Years resolution: no more gun projects!!

  • Dr Motown March 9, 2018, 7:16 am

    Love Odin Works! Met them at the NRA meeting a couple years back and was sold on their ultra-light hand guards and adjustable gas blocks. Back then, they were also a bit cheaper than BCM

  • ed anderson March 9, 2018, 6:11 am

    You forgot all the things required to fasten the barrel to the receiver in your parts list! Also, nice to use head space gauges to ensure safety should be in listed tools.

  • Jaque Bauer March 8, 2018, 2:23 pm

    I don’t think Eugene Stoner could have envisioned the huge industry that sprang up around his design of the AR platform. When I purchased my first AR15 in 1976 Colt was the only maker, as it held the patent rights. The only accessory at the time was a bayonet and a cleaning kit and a 4 power scope. Back then I was the only guy at the range with a plastic rifle. It was a novelty then and the owners of traditional wood and steel rifles didn’t like it and the “twang” it made as the buffer spring vibrated. I have no idea how many makers of the AR there are today, but I bet there’s at least a dozen. Since then I’ve built a carbine from parts and bought another Colt rifle, an AR15A4. So many guns and so little time to shoot em.

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