It’s always interesting to see which articles really resonate with readers on our site. Some reviews and “How-to’s” fade quickly while others stay popular for years. One such article is “How to build an AR-15: A Beginner’s Guide” by Nate Schultz. It was published in July of 2017 and still regularly registers enough clicks to stay on the “What’s Hot” list on our homepage. Clearly, a lot of readers are interested so I thought a somewhat more advanced follow-up would be appropriate. Here it is, How to build an AR-15: Advanced upgrade options edition, Part 1.
In this, Part 1, we’re going to cover the receivers (upper and lower), as well as barrels. Due to the incredibly technical nature of some of these parts, this will be considered a primer, not an exhaustive report on every subject.
First, let’s set the stage. Assuming that after reading the beginner’s guide, you checked local laws, purchased entry level parts, receivers and a build kit. You’ve assembled yourself a bare-bones AR-15, likely with a 16″ barrel chambered in .223/5.56. You’ve enjoyed this rifle, but it’s time to move up. Here are many of the options you can consider, with some care to note the likelihood of each upgrade damaging your wallet.
(Note, I don’t get any kick-backs for listing links to any of the products below. There are MANY different companies to choose from, if you don’t like the ones I link to, do some research on alternatives. Your bucks, your choice.)
Know your role:
It’s a good idea to narrow your (nearly countless) options by focusing on a specific end goal. Many want to get into long range shooting, where a caliber change to 6.5 Grendel or 6.8 SPCII might be warranted. If you’re short, noise averse or want to maximize the effectiveness of your suppressor, a change to .300 Blackout might be ideal. Aside from caliber changes, other major role changes might be: 3-Gun competition, building an Ultralight rifle or maximizing accuracy for benchrest shooting. Planning ahead will help prevent the purchasing of unnecessary or redundant parts. Once you’ve got your game plan, consider each upgrade’s overall effect. A hunting rifle that’s excessively heavy due to a bull barrel and heavy fore-end is a pain in the ass to lug up a mountain, for example.
In no particular order, here’s a litany of items to consider.
RECEIVERS:
The upper and lower receivers themselves are the backbone of the rifle system. If you have an old carry handle and want modern optics mounting options, get yourself a flat-top upper receiver like this one from Brownells. While M4 feed ramps are standard on most uppers, I like to double check that any upper I purchase has them. They aid the bullet in feeding into the barrel, reducing stoppages.
There’s also cosmetic choices in receivers, like those from Sharps Bros, pictured below.
We also have receivers that use non-standard materials in their composition, such as polymers or high-tech alloys. Polymers are generally seen as light-weight, inexpensive (or plain cheap) and less durable than most metal alternatives. One example is the fiber reinforced nylon receiver with brass inserts by Tennessee Arms Company. Their lower runs ~$45.
V Seven Weapon systems is one of the better-known manufacturers using alloys in their parts. Alloys like titanium, magnesium and 2055 Lithium-aluminum are often lighter, stronger and more corrosion resistant than 6061 or 7075 aluminum more commonly used. The downside to shedding weight? Cost. The expense in procuring and machining harder metals leads to those receivers being considerably more expensive. V7’s Enlightened lower receiver runs ~$360.
Also see: Fostech, 2A Arms for alloyed, New Frontier Armory or GWACS Armory for polymer.
Additionally, we have receivers with function upgrades, such as those offering built-in ambidextrous controls (mag release, bolt-stop, safety). The two I’m most familiar with are Radian Weapons AX556 lower with ADACS controls (~$370) and some of Noveske’s Gen III and IV lowers (not factory sold separately though sometimes on the ‘net). Also available is San Tan Tactical’s ambi lower, ~$275.
BARRELS:
The options here are vastly numerous. Like I touched on in the intro, the barrel (more than any other part) dictates what your gun does, and how well. While .223/5.56 will always be the default chambering of the AR-15 platform, a number of other calibers have attained widespread adoption. The differences between various barrels within the same category relative to each other are:
- Length: More = faster muzzle velocity, less = lighter and more maneuverable. Despite popular misconceptions, a longer barrel isn’t necessarily a more accurate barrel. Length gives velocity, but a short barrel can be just as accurate.
- Twist: Faster twist rates are better for heavier bullets. For example, Q’s 7″ Honey Badger, which features a 1:5 twist, favoring heavy (for it’s caliber) 220 gr subsonic rounds, whereas V7’s 6.5″ barrel with a 1:7 twist does very well with lighter 110 gr supersonic rounds.
- Profile: Usually it’s simply a diameter such as Bull Barrel versus Pencil Barrel, but can be more specific such as M4 profile or SOCOM M4, both of which have varying diameters and “steps” along the length of the barrel. Pay attention to the diameter of the gas block journal, or the diameter of the barrel under the gas block. .750″ is the standard, with some Pencil barrels (like Faxon‘s) having a thinner .625″ journal and some Bull barrels (like Stag Arms) having a thicker .936″ journal. This matters big time when selecting your gas block later on. Some barrels will also have fluting or geometric shapes machined onto their exterior, to decrease weight and increase thermal transfer off of the barrel. A thicker barrel will change temperature more slowly, keeping it more consistent for longer strings of fire. I can get my pencil barrel hot very quickly, at which time the point-of-impact starts to shift noticeably.
- Gas system length. Determines how far down the barrel the gas port is drilled. This affects “dwell time”, or the amount of time the bullet is still in the barrel after having passed the gas port. If we take an imaginary barrel, let’s say 16 long and could choose where to drill the port, a pistol length system (4″ long) would have drastically higher gas pressure blowing back into the receiver than a Carbine length (7″) or Mid length (9″) system, causing excess recoil and possibly inducing malfunctions or damage. Conversely, that same barrel would have lighter recoil with a Mid length system than with a Carbine length, so long as there’s still enough gas to cycle the system. Generally the manufacturer will select the gas system length that works most often under the widest variety of circumstances when they make the barrel- but there are options out there.
- Gas port diameter: Here’s a little fact not every rifle buying customer knows… many manufacturers run with wider gas ports than is necessary, to make the rifle run more reliably with the widest variety of ammo possible. They’d rather the gun was “overgassed” than have malfunctions due to a poor ammo-barrel combo. But as we’re talking about more than a basic guide, this is well worth covering. Even if you don’t reload (but especially if you do). Due to the myriad possible caliber/barrel length/gas length combos out there, I can’t cover every one. But it is worth doing some specific reading on the topic if you want to fine tune your system, especially if you plan to run a dedicated suppressed system. Using an adjustable gas block/bolt carrier/gas key (covered later) will reduce the gas blowback, cycling the rifle softer for less recoil and less of a gas cloud near your face. Over time, excessive gas (and the resulting excessive bolt carrier velocity) can also cause premature wear on parts.
- Rifling type: There are a few rifling types to cover. Rifling is the cut pattern on the inside of the barrel that imparts spin upon the projectile. Traditional rifling is a spiral cut with lands (high points) and grooves (low points). Traditional rifling is still the standard, and performs very well compared to upgrades. 5R rifling is a newer type, which reduces bullet deformation as it travels down the barrel. It is alleged to have higher accuracy potential, and many users have commented it as much faster to clean as it has significantly less copper fouling building up in the barrel.
- Steel type: There are essentially four categories of barrel steel/coatings: Chrome Lined, Chromoly, Stainless and QPC AKA Melonited. Chrome-lined is usually made from 4140 or 4150 steel and the bore is lined with hard chrome, then the barrel is finished with parkerizing on the exterior. Usually considered to be best for high-volume and high-rate firing schedules. Generally not as accurate as Stainless.  Chromoly (CMV) is often the same metal, with some Vanadium added to protect from corrosion but with no chrome lining.  A little more accurate than Chrome-Lined but shorter life. Usually cheapest.  Stainless steel is the best option for precision, and has excellent built-in corrosion resistance except it’s usually more expensive than the first two options covered.  Melonite barrels are also usually 4140 or 4150 steel and dipped in a salt bath that leaves the steel very resistant to rust and corrosion but without the surface imperfections that degrade a Chrome-lined barrel’s accuracy slightly.
- Chambering:  This is caliber specific. I can give some examples for you to reflect on and study further if needed. The chamber is where the loaded round rests, leading up to the rifled part of the barrel. Even within calibers, there may be more than one chambering available. The most well known example is .223 Remington (ammo, chambering), versus 5.56 NATO (ammo, chambering), versus .223 Wylde (just a chambering). A barrel chambered in .223 Remington can safely fire a bullet labeled the same, but may not safely fire a bullet labeled 5.56 NATO due to pressure differences. A barrel chambered in .223 Wylde has been designed to safely fire both .223 Remington and 5.56 NATO. There are other caliber-specific instances (such as 6.8 SPC versus 6.8 SPC II) where more than one chambering exists. If you’re venturing into a caliber that’s new to you, check to see if any variants exist.
While there are countless barrel manufacturers out there today, a few of the most popular are Ballistic Advantage, Faxon, Odin Works, Noveske and V Seven.
This brings us to the end of part 1. Hopefully, the novice rifle builders out there have found a few nuggets of information to consider as they move towards a more advanced skillset and discerning eye toward parts. Join me again in How to build an AR-15: Advanced upgrade options edition, Part 2, (coming soon) as I cover forends, gas blocks, bolt-carrier groups and charging handles in depth.
