Aero Precision What You Need AR-15 Building Videos

Apr 15, 2020 | AR-15 Technical

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What you will need after buying an AR15 Stripped Lower Receiver Video

What you will need after buying an AR15 Stripped Lower Receiver

Kirk from Aero Precision reviews the components you will need for building out your AR15 Stripped Lower Receiver to complete your lower receiver assembly. Components reviewed include the lower receiver, lower parts kit, buffer kit, stock/brace and magazine.
Stripped Lower Receiver : When building an AR15 Lower Receiver, the first thing you will need is a stripped lower receiver. This is the registered part of the AR15 so it will need to be transferred or purchased through an FFL Dealer. The lower receiver is the portion that contains the fire control group, magazine, and buffer assembly. We offer two variants of AR15 lower receivers, the M4E1 and the X15/AR15 Gen 2. Both are compatible with mil-spec components.
Lower Parts Kit: The lower parts kit includes the smaller components needed to complete your stripped lower receiver, such as pins, springs and detents. We offer several options as complete lower parts kits which include a fire control group (trigger) and grip. If you want to use an upgraded trigger, pistol grip, or trigger guard you can buy the lower parts kit without these components included. We also have specific M4E1 Lower Parts Kits that do not contain a trigger guard as the M4E1 Stripped Lower Receiver features an integrated trigger guard.
Buffer Kit: The buffer kit attaches to the rear of the lower receiver and contains a buffer tube, buffer, buffer spring, castle nut, and endplate. You will need an AR15 Buffer Kit that will accommodate whichever stock you choose for the build. Most standard AR15 builds using a collapsible stock will use a carbine buffer kit. We also offer rifle buffer kits for use with fixed stocks and pistol buffer kits for use with arm braces.

Stock or Arm Brace: Choose a stock or arm brace to complete your lower build. Your stock or brace will install over your buffer tube. Please ensure you are in compliance with all local and federal laws when selecting either a stock or arm brace.

Magazine: The magazine is the component of the AR15 that holds your ammunition. Please ensure you have the appropriate magazine for whichever caliber you choose to build (5.56 NATO, .223 Rem, and .223 Wylde all utilize the same magazine).

Once you get the parts you need, you are ready to start building! If you are uncomfortable with the building process you can always take your components to a local gunsmith or armorer to have your lower receiver assembled. We do also offer complete AR15 lower receivers on our website if you prefer to purchase as an assembly.


What you will need after buying an AR15 Stripped Upper Receiver Video

What You Will Need After Buying an AR15 Stripped Upper Receiver


Watch the “What you will need after buying an AR15 Stripped Upper Receiver” at


Kirk from Aero Precision reviews the additional components you will need after purchasing an AR15 Stripped Upper Receiver. Components covered include the upper receiver, bolt carrier group, charging handle, barrel, muzzle device, gas tube, gas block and handguard.
Stripped Upper Receiver: The first thing you will need for an AR15 Upper Receiver build is either a stripped OR assembled upper receiver. If you purchase a stripped upper receiver you will also need to purchase an upper parts kit which includes the forward assist and dust cover assembly. These components are already installed on an assembled upper receiver.
Bolt Carrier Group: The bolt carrier group (BCG) is the heart of the AR15. It houses several critical components including the bolt and firing pin. The bolt in the BCG is caliber specific so make sure you buy the appropriate one (.223/5.56 and .300 Blackout use the same bolt). They primarily come in 3 finishes: nickel boron, black nitride, and phosphate. Phosphate is the standard bolt carrier group finish that has been industry standard for decades. Nickel boron is generally easier to clean, generates less friction than phosphate and looks silver in color. Black nitride has some of the same added benefit as nickel boron but maintains a black finish.

Charging Handle: The charging handle is used to manually charge the action of the firearm. These are available in standard configuration with a single lever on the left side, as well as ambidextrous configurations with activation levers on both sides.

Barrel: Barrels come in a variety of lengths to meet the end user’s needs. Barrels are caliber specific, meaning you will need to use the proper one for the caliber you are trying to shoot (.223 Wylde and 5.56 barrels are both able to shoot 5.56×45 as well as .223 Rem). Barrels also come in different finishes. The two primary finishes we offer are Stainless Steel, and Chrome Moly Vanadium (CMV). CMV is a corrosion resistant finish that is black in color. All Stainless Steel barrels we offer have a bead blasted finish.

AR-15 chamberings offered by Aero Precision:

Muzzle Device: The muzzle device threads onto the end of your barrel and functions as a way of directing gas as the projectile is leaving the muzzle. There are flash hiders which mitigate flash, as well as muzzle brakes that help mitigate recoil and muzzle climb when firing. Each different muzzle device has its own set of benefits and is very much so a personal choice. You will need to ensure that the muzzle device you choose corresponds to the caliber and thread pitch of the barrel you purchase. We offer the entire VG6 Precision line of muzzle devices as well as standard flash hiders.

Gas Tube: In a direct impingement rifle such as the AR15, the gas tube functions as a passage that directs the gas from the fired cartridge back to the gas key of the bolt carrier group to cycle the action. Please ensure the gas tube length you select is the proper size for the barrel you purchase. They are generally available in 4 lengths: pistol, carbine, mid, and rifle. The length of gas system is entirely dependent on what barrel you purchase.

Gas Block: The gas block attaches to your barrel and is what guides the gas from the gas port in the barrel to the gas tube. Please ensure the gas block is sized to fit the gas block journal on your barrel. The gas block journal is the section of the barrel where the gas block rests. Common gas block sizes include .625, .750, .875 and .936 with .750 being the most common. The gas blocks we offer are low profile, meaning they are small enough to fit under most free float handguards. Our gas blocks also contain the gas block set screws required for mounting.

Handguard: The handguard slides over the barrel and attaches to your upper receiver. It protects your hand from the heat of the barrel when shooting while providing mounting solutions for accessories such as sights, bipods or flashlights. The handguard is very much so a personal choice. We offer them in several different lengths and configurations. Below are a few things to note about our offerings:

  • The Aero Precision Enhanced Handguard is designed to interface directly with the M4E1 Enhanced Upper Receiver. If you would like to use it on a standard threaded upper receiver, you must also purchase a BAR Barrel Nut.
  • All Aero Precision ATLAS Handguards will include a barrel nut that is compatible with standard AR15 upper receiver threads.
  • The Aero Precision ATLAS Handguards come in two configurations: the ATLAS R-ONE which features a full top picatinny rail that runs the entire length of the handguard, and the ATLAS S-ONE which has the center rail machined down for reduced size/weight with only a small picatinny section on each end of the handguard (enough to mount a front sight or similar accessory).
  • The Enhanced Handguards and ATLAS Handguards are available with M-LOK® slots on the sides and bottom of the handguard to allow attachment of rail sections where you need them for flashlights and other accessories. The Enhanced Handguards are also available in a Quad Rail version with picatinny rails on all 4 sides.

Once you get all the parts you need, you are ready to start building! If you are uncomfortable with the building process you can always take your components to a local gunsmith or armorer to have your upper receiver assembled. We do also offer complete AR15 upper receivers on our website if you prefer to purchase an assembly. Upper receivers can be shipped directly to your home as long as there are no controlled items on the same order.