AR-15 BUFFER TUBE AR-15 LOWER RECEIVER EXTENSION TUBE
The AR-15 Buffer Tube also known as the “Receiver Extension Tube” is the long hollow tube that extends from the lower receiver. The buffer tube serves several purposes.
The first purpose is to house the AR-15 lower receiver recoil components which consist of the buffer and buffer spring. The second purpose is for the mounting of the rifle stock.
AR-15 CARBINE BUFFER TUBE, Milspec or Commercial?
AR-15 carbine stock buffer tubes are available are available in two different diameter, Milspec and Commercial. The 1.170″ commercial AR-15 buffer tube is smaller in diameter than the 1.185″ mil-spec. When replacing the stock on an AR-15 it is important to know which buffer tube your weapon has. A milspec rifle stock will wobble on a commercial buffer tube. A commercial rifle stock usually will no fit on a milspec buffer tube. There is no standard on which type ships with factory new rifles. Colt carbine rifles ships with Milspec, DPMS carbines ship with commercial tubes.
When specifying and selecting new buttstock parts for you AR rifle always choose milspec. The reason being more options and strength. Note: The tube threads are the same.
Download Receiver Extension Identification and Technical Drawings Below
- AR-15 Commercial Receiver Extension Tube Dimensional Drawing
- AR-15 Milspec Receiver Extension Tube Dimensional Drawing
- AR-15 Receiver Extension Tube Identification | Buffer Tube Identification
AR-15 BUFFER TUBE/AR-15 LOWER RECEIVER EXTENSION TUBE,
TUBE LENGTH, CARBINE vs RIFLE, A1 vs A2
In addition to tube diameter the AR-15 lower receiver extension/buffer tube selection is compounded by different lengths and styles. For the purposes of this page we will discuss the most common, A1 rifle length , A2 rifle length and carbine (adjustable).
The A1 Rifle versus A2 Rifle discussion actually has nothing to do with the receiver extension tube. It is only used in reference to the length of fixed rifle stocks. An A2 rifle stock needs an an a2 spacer and longer screw to attach the fixed stock to the lower receiver extension tube. The A2 fixed rifle stock will screw directly to a lower receiver extension.
CARBINE LOWER RECEIVER EXTENSION TUBE/BUFFER TUBE
Note: For the purposes of this site the following details apply to standard AR-15 rifles and not AR-10 or 308 AR rifles.
Carbine length lower receiver extension tubes are shorter than tubes for fixed rifles. The carbine buffer tubes are keyed for their entire length. This key performs to functions. The first function is to prevent the AR-15 rifle stock from rotating. The second function is to provide the detents for the stock locking mechanism for the 6 position (typically) presets. Remember from above, the carbine length lower receiver extension tubes are available in commercial or milspec diameters.
Note: When replacing an AR-15 stock be certain to use the correct buffer and buffer spring for you caliber and rifle stock selection.
PWS Enhanced Buffer Tube Gen 2 AR-15 Buffer Tube
PWS Enhanced Buffer Tube MOD 2 – With the AR-15 market completely saturated with hardware we are now seeing a lot of effort put into appearance and improvements. These AR-15 improvements are questionable at best. It’s refreshing to see one of the most simple parts of an AR15, the BUFFER TUBE undergo a clever and FUNCTIONAL redesign. Primary Weapons Systems has accomplished this in their PWS Enhanced Buffer Tube MOD 2.
- PWS has made a RECEIVER EXTENSION TUBE that’s corrosion resistant, lighter and stronger. The PWS Enhanced Buffer Tube Gen 2 AR-15 Buffer Tube is optimized for strength and rigidity while creating a solid platform for the new lightened design. Anodized in Mil spec type 3 to exceed standards in hardness and corrosion protection.
- The new Ratchet-Lock Design eliminates the need for staking the castle nut and gives a rock solid lock up while being able to remove it easily if needed in the future.
- Additional lightening cuts reducing weight in conjunction with the new attachment design net nearly a 1oz weight reduction from already efficient mil spec buffer tube design.
- The anti-tilt lip enhances function and reliability, giving longer life to piston driven weapons by allowing the carrier to start in the buffer tube rather than transitioning into the tube on extraction.
The PWS Enhanced Buffer Tube MOD 2 features a ratcheting castle nut. Gone is the need for castle nut staking. This makes disassembly easy. The BUFFER TUBE has an extended lip called the “Anti-Tilt Lip”. This allows the bolt carrier to start it’s motion in the BUFFER TUBE and eliminates carrier tilt.
AR-15 Receiver Extension Tube – PWS Enhanced Buffer Tube MOD 2 Details:
- Material & Coating – Impact extruded from 7075, the PWS EBT is optimized for strength and rigidity while creating a solid platform for the new lightened design. Anodized in Mil spec type 3 to exceed standards in hardness and corrosion protection
- Ratchet-Lock Design – The new Ratchet-Lock Design eliminates the need for staking the castle nut and gives a rock solid lock up while being able to remove it easily if needed in the future.
- Reduced Weight – Additional lightening cuts reducing weight in conjunction with the new attachment design net nearly a 1oz weight reduction from already efficient mil spec buffer tube design.
- Anti-tilt Lip – The anti-tilt lip enhances function and reliability, giving longer life to piston driven weapons by allowing the carrier to start in the buffer tube rather than transitioning into the tube on extraction.
- Stock – Featuring six stock positions with enhanced drainage ports for greater reliability regardless environment or application.
- QD Mounts – The central QD sling swivel mount allows for neutral positioning of your firearm with multiple sling configurations.