Some home builders might refer to an assembled upper as an AR15 upper build kit; in both cases, the upper or the kit will come with all of the parts needed to create an entire assembled upper for an AR.
By the letter of the term, the build kit will just contain parts and the assembled upper would be ready to go. Either way, if you’re looking at an AR15 upper build kit, here’s what it should contain.
A Stripped Upper Receiver
The stripped upper receiver itself, made from aluminum, is the component that receives all of the other parts of the upper, hence the name. It also houses the bolt carrier group.
A Barrel
Obviously no AR upper build kit could be called such without containing a barrel. This is the component responsible for trapping gasses to accelerate the bullet out of the gun.
If the Barrel Is Threaded, a Muzzle Device
For any barrel that is threaded, the kit will also likely contain a muzzle device; the most common option is a flash hider, but there is also a chance the kit comes with a component known as a muzzle brake, the purpose of which is to reduce recoil. If the barrel is threaded and does not come with a device it should come with a thread protector installed.
A Gas System
The gas system is the component that is responsible for cycling the action, on which the rifle depends for autoloading operation. It is usually attached to the barrel, though some are adjustable and have components that can be fairly easily replaced.
A Handguard
The handguard is the part that enshrouds the barrel, both protecting a user’s hands from contact with a hot barrel or gas system, and serving as an attachment point for a multiplicity of accessories. Common handguard systems include Picatinny, KeyMod and M-LOK handguards.
A Bolt Carrier Group
The bolt carrier group is the reciprocating component that loads the action, fires the gun, and the extracts and ejects spent casings. Most build kits come with them but not all do so pay close attention before buying.
A Charging Handle
The charging handle is used to manually cycle the action. This is another component that is sometimes not included with AR upper build kits, so look closely.
A Forward Assist
The forward assist is used to return the bolt carrier group to battery if the action fails to close completely, and is usually contained within complete build kits.
An Ejection Port Cover
The ejection port cover, also known as the dust cover, is a component that covers your ejection port, protecting the action and bolt carrier group against moisture and dust ingress. This is another component not always included in AR upper build kits. Also, side-chargers typically do not have (or need) ejection port covers.
All Applicable Upper Hardware
Lastly, a complete AR upper build kit should come with all hardware necessary to assemble the upper, including the barrel nut, screws and other fasteners, pins and springs. Make sure of this before buying, and make sure you have the tools on hand you need to assemble the upper once you have the kit.
Where to Explore Options in AR15 Upper Build Kits
One note here is that it’s important to realize that even with a fully assembled upper, you cannot complete a functioning rifle. For that you need a lower receiver as well as a lower parts kit.
In any case, you can get most of the parts you need (minus the lower receiver, which is the action firearm) over at MCS Gearup. Check out their collection and get in touch with them at [email protected] if you have any questions.
For more information about Glock Kits and Micro Roni Please visit: MCS Gearup.
