One of the most attractive elements of “America’s Rifle” is that it is so highly modular. You can take off almost any part of an AR, stick a new one on from a different manufacturer, and as long as the specs are all the same, carry on your merry way.
There are many aftermarket parts producers, and no shortage of parts compatible with AR platforms, or with other modern sporting rifles, for that matter.
One thing you’ll have to decide, when you make your own rifle, is whether or not you want to build one from a complete AR 15 upper or buy the upper parts separately and then assemble them.
If you go the latter route, here are some key considerations to make regarding the main parts of an upper assembly.
AR 15 Barrels
The type and length of the barrel you choose for your AR is one of the most important considerations you can make, as your choice of barrel will impact muzzle velocity, accuracy, handling, and maintenance.
The original AR-15 was designed and made with a 20” barrel, and this is a size that many people still choose today. A 20” barrel will produce the highest muzzle velocity, the greatest ballistic performance, and the flattest trajectory. Also, a 20” barrel produces a longer sight radius, handles well, and since it increases the mass of the rifle, can cut recoil. With that said, a 20” barrel can produce a rifle that is slightly muzzle-heavy, and will not handle as nicely at close ranges.
Other popular options include 18” and 16” barrels. The 16” barrel is probably the second most popular after a 20”, and lightens the rifle while still producing good accuracy. They’re also much less muzzle-heavy and easier to handle at close ranges.
Any rifle with a barrel less than 16” would be considered an SBR (short-barreled rifle) which is an NFA item, so your three main options will be 20”, 18”, and 16”, with 20” and 16” most popular for the reasons mentioned.
You will also need to give some thought to barrel finish. Two of the most common barrel finishes are parkerized and nitrided. Both finishes protect against corrosion, but nitrided barrels probably offer slightly better protection. A nitrided finish is very hard, wear and scratch-resistant, and exhibits excellent permanent dry lubricity, making them easier to wipe clean with less need for harsh bore solvents.
AR 15 Muzzle Devices
If you get a complete AR 15 upper with a threaded barrel, you will also want to give some thought to muzzle devices.
If your barrel has threads, you should always run it with a muzzle device. If you don’t, you run the risk of damaging the threads, so if you don’t run a muzzle device, install a thread protector.
Otherwise, there are three main types of muzzle devices. The first of these is called a flash hider. A flash hider conceals the muzzle flash of a shooter, helping him or her to conceal a disposition.
Another popular muzzle device is known as a muzzle brake (which on a handgun would be called a compensator). Muzzle brakes disperse gases at the muzzle, counteracting the effects of felt recoil. A good muzzle brake can diminish felt recoil by as much as 50% (or more) without affecting shot power.
Another class of muzzle device is a suppressor, which is also popularly referred to as a “silencer” or informally as a “can.” Suppressors trap expanding gases at the muzzle and reduce muzzle pop, but trap a lot of fouling in the barrel and action.
Handguards and Rail Systems
You will also have to choose a handguard for your AR build, if you don’t go with a complete AR 15 upper.
The handguard is the part that covers the barrel and serves as a forward grip, since AR-style rifles don’t have traditional forends.
Some handguards, like tropical handguards, serve only as a grip and have few (to no) attachment points. Other handguards double as rail systems.
One of the most popular types of rail systems is a Picatinny rai systeml, which consists of dovetail angles and grooves which allow for the mounting of shooting accessories like lights, lasers, and optics. The majority of rail systems are probably Picatinny rails.
Two popular alternatives to Picatinny rail systems are KeyMod and M-LOK rail systems. Both are much lighter and lack the sharp edges of Picatinny rail systems, and consist of slots machined into an aluminum body. They also both require specific accessories, and there are fewer for them, but there are still plenty to choose from and more are being developed every year.
Bolt Carrier Groups
Some AR 15 upper assemblies do not come with bolt carrier groups, so in some instances, you will need to choose your own.
One primary thing to consider in a bolt carrier group is what type of finish it has. There are a wide range of modern finishes offering superior wear and corrosion resistance, along with permanent dry lubricity.
Two common bolt carrier group finishes are hard chrome and black phosphate. Both are durable and corrosion-resistant. The phosphate coating may also be referred to as mil-spec, and it has more tooth than hard-chrome. Despite being highly cost-effective, a phosphate finish will be harder to clean and require more maintenance than a hard chrome BCG.
There are many other modern bolt carrier group coatings. One is black nitride, also referred to simply as nitride. This finish offers excellent wear and corrosion resistance and offers great permanent dry lubricity, making it easier to clean without the need for excess liquid lubrication. It is, however, more expensive than phosphate.
Other advanced finishes include nickel boron, titanium nitride, and DLC (or diamond-like carbon). All three of these offer excellent wear and corrosion resistance and have super-slick surfaces with low coefficients of friction. They exhibit excellent permanent dry lubricity, making them easier to clean and requiring minimal liquid lubrication, but they are much more expensive than hard chrome, phosphate, and even black nitride finishes.
Complete AR 15 Uppers and Parts
MCS Gearup carries a wide range of complete upper receiver assemblies with different barrel lengths, complete with gas systems, charging handles, ejection port covers, forward assists, and more.
If you have any questions about our AR 15 uppers (and the differences between them) before starting your build, contact us at Sales@MCSGearup.com. We’ll help you get started.