Select the Chambering for your Build

Build your AR-15

Centerfire Cartriges using Imperial measurment

.223 Remington

300 Blackout

300 Whisper

350 Legend

375 SOCOM

400 Legend

450 Bushmaster

458 SOCOM

.50 Action Express

.50 Beowulf

There are a great many calibers that the AR-15 platform will support. Many of these calibers are not "mainstream" but the AR-15 can be built to handle them all. For the sake of mitigating confusion we will not consider any of the "Wildcat" calibers and focus on those chamberings that are most common and readily available. For a complete listing of all compatible calibers please see: List of AR platform cartridges - Wikipedia

These are the centerfire calibers that are most common among AR-15 builders:

Centerfire Cartriges using Metric measurment

5.56 x 45 NATO

5.7 x 28

6mm ARC

6.5mm Grendel

There are several Rimfire Cartriges that can be used on the AR platform as well but I have excluded them from the list as they are not common calibers for the AR-15, although it should be noted that several of them make really good varmint rifles for groundhog and other pests.

Select the Platform format and the Barrell Length for your Build

There are four distinct barrel lengths for the AR-15:

Rifle Length is generally any barrel length above 18". Rifle length barrels are typically 20" to 24" and are designed for long range shooting.

Mid-Length is generally any barrell length between 16" and 18".

Carbine Length is generally a 16" length barrell and is the most common barrel length.

Pistol Length is any length below 14.5" - It should be noted that there are special rules concerning the pistol length AR-15.

The reason I break the barrel lengths into these catagories is that the Gas Tube lengths for each of these formats is different and has an impact on the proper buffer spring tension and buffer weight to be used based on the caliber of the cartridge that is to be used.

It should also be noted that some chamberings can be had with more than one Gas tube length. The 300 Blackout for example is available with a Carbine length Gas Tube as well as with a Pistol length Gas Tube. The distinction here is the purpose of the weapon. If you want to run the 300 Blackout with a silencer that would mean you need to run 180 to 220 grain bullets to keep the projectiles subsonic and you will need to use a Pistol Gas Tube type barrell in order for the weapon to cycle properly. If on the other hand you were not going to add a silencer you could just run the Carbine Gas Tube type barrell. It should be noted that you can run both subsonic and supersonic rounds in an unsuppressed barrel.

Choose your Upper and Lower receivers

While there are many manufacturers of upper and lowere receivers, not all of them are made the same.

We have found several manufacturers that pay close attention to detail, have good quality control and deliver parts that are function perfectly.

The following manufacturers have provided me with excellent building blocks for well built weapons.

1) Anderson

2) Aerotech

3) Wilson Combat

While there are many companies that manufacture upper and lower receivers that are also reputable, these are our choices. The Anderson is le least expensive while the Wilson Combat tends to be the most expensive and the Aerotech in in the middle on cost. They all are good choices for building a great rifle.