Most modern firearms have a component called a receiver to which all other major parts, including the action, barrel, stock and trigger assembly attach. That is why it is called a receiver; it “receives” all the other parts. 

That being said, modern sporting rifles, like AR15 rifles, have two receivers, an upper and a lower, which are associated with different parts. Here’s what you should know about what comes with an AR15 upper build kit (or what should come with one) if you are considering going that route for building a rifle at home. 

• Upper receiver. Obviously an AR15 upper build kit should come with the upper receiver itself. This is because the upper receiver is not considered a firearm, only the lower is. Because of this note, it is important to remember that if you get a lower build kit, it won’t come with a lower because that part requires an FFL transfer and a NICS check. 
• An AR15 upper build kit typically also comes with a handguard that either sports a Pic rail or M-LOK rail system for mounting shooting attachments. 
• An AR15 upper build kit should come with a barrel which is a critical component. This one is a part you might also want to swap out depending on what you want in terms of barrel length or performance, or if you want a fluted barrel that will shed weight. 
• Barrel nut. The barrel nut is a piece of hardware that secures the barrel to the receiver. 
• Gas system. The gas system, which consists of a gas block and tube, is responsible for siphoning off some gas from the barrel, back to the bolt carrier group’s gas key, so that it can cycle the action. 
• Muzzle device. Most AR15 upper build kits come with threaded barrels that have flash hiders already installed. This also gives you the flexibility to install a different muzzle device like a brake or a suppressor if you so choose. 
• Charging handle. The charging handle is used to manually manipulate the action of the rifle. Most but not all upper build kits come with one. 
• Ejection port cover. The ejection port cover, also known as a dust cover, is a component that keeps dust and debris out of the open action of the rifle when it is in operation. 
• Forward assist. The forward assist is a plunger or button like component that can be used to fully close the action of the rifle if for some reason the bolt carrier group ever does not fully return to battery. 

An AR15 upper build kit may also come with a bolt carrier group, but this is not always the case so make sure you check the kit specifications before you buy.

Need More Information (Or Here for an AR15 Upper Build Kit)? 

Want to learn more about AR15 upper build kits, or see what’s at your disposal in terms of options? Check out MCS Gearup. They carry a wide range of build kits in addition to parts for AR builds and customization projects. Visit their website and get in touch with them if you have any questions before you buy.

For More Information About M Lok Rail System and Ar15 Pistol Upper Please Visit: MCS Gearup.