FAXON RIFLE LENGTH STAINLESS STEEL AR GAS TUBE

Why 304 Seamless Stainless

The gas tube is the hottest, dirtiest, least-seen part of an AR. Every shot sends propellant gas at several hundred degrees down a tube about the diameter of a pencil, and carbon condenses on the inside of it. The tube has to survive that without rusting, without scaling, and without letting carbon bond to it, and it has to do so with no coating to wear off.

304 is the stainless alloy for that job. It is austenitic, so it does not lose corrosion resistance when heated the way some hardenable stainless grades can, and its chromium oxide surface stays passive through repeated heat cycles. It is the same alloy family the mil-spec gas tube has always been made from. Faxon uses it bright and uncoated: there is nothing to chip, flake, or thin out where the tube meets the gas key.

Seamless matters because of how tubing is made. Welded tubing starts as flat strip, rolled round and welded along its length; the seam is a different microstructure from the rest of the wall and leaves a bead or a flat inside the bore unless it is removed. Seamless tubing is drawn from a solid billet, so the wall is one continuous piece with uniform thickness and a smooth interior. In a gas tube, that means no seam to corrode preferentially, no rough spot for carbon to build on, and a tube that stays straight under the heat of a long string of fire.

What’s in the Box

Which Gas Tube Length Do You Need?

The gas system length is a property of the barrel, set by where the gas port is drilled, and the tube has to match it exactly: too short and it never reaches the gas block, too long and it will not seat in the receiver. Barrel length only tells you what is typical. The table below covers the four standard systems; each row links to that tube.

Installing a Gas Tube

1. Remove the old tube. With the gas block off the barrel, drive out the roll pin with a 1/16″ punch and slide the tube out of the block. Discard the pin.
2. Orient the new tube. The gas port hole in the tube faces down, toward the barrel, and the pin hole runs side to side. The flared, slotted end goes toward the receiver.
3. Seat it in the gas block. Slide the tube into the block until the pin holes line up. Look through the block’s pin hole to confirm the tube’s hole is centered.
4. Drive the new roll pin. Start it with a roll pin holder or a pair of pliers, then seat it flush with a 1/16″ punch. The tube should not rotate or slide in the block.
5. Install the block and check alignment. Set the block on the journal with the tube passing through the barrel nut and into the receiver. It should enter the gas key with no side load; if it binds, the block is rotated. Square it, torque the set screws, and function-check.

If you are installing a Faxon adjustable gas block at the same time, install the tube in the block first, then set the block on the barrel; the block’s instructions cover set-screw torque and alignment.

Faxon Rifle-Length Gas Tube FAQs

Which barrels take a rifle-length gas tube?

Any barrel whose gas system is listed as rifle-length. That is normally 18″ to 24″ barrels, but go by the barrel’s spec, not its length: the gas system is set by where the port is drilled, and every Faxon barrel page states it. The tube itself is about 15.125″ long.

Does it fit an AR-10 / LR-308?

Yes. AR-10 and LR-308 rifles use the same gas tube as the AR-15, in the same four lengths. The gas tube diameter, the gas block bore, and the gas key on the carrier are shared between the platforms, so this tube fits either.

What is the tube made of, and why does it matter?

304 seamless stainless steel tubing. 304 is an austenitic stainless that handles the heat and carbon of the gas system without a coating and without rusting. Seamless means the tube is drawn as one piece rather than rolled from strip and welded, so there is no seam in the wall to become a weak point or a rough spot inside the bore.

Is a roll pin included?

Yes. Every Faxon gas tube ships with its installation roll pin. Use a new pin each time a tube is installed; the old pin deforms on the way out.

Will it work with the Faxon adjustable gas block?

Yes. The Faxon adjustable gas block moves the gas tube itself to meter gas, and it uses a standard gas tube in any length. This is the tube to pair with it.

How do I know it’s time to replace a gas tube?

Short-stroking or failures to lock back with a clean, well-lubricated rifle and known-good ammunition; a tube that is bent, kinked, or scored at the receiver end; heavy carbon that will not clear with a pipe cleaner and solvent; or erosion at the gas-block end after very high round counts. A gas tube is a wear item on a hard-used rifle and one of the cheapest fixes there is.

Bright stainless or black?

Faxon gas tubes are bright, uncoated 304 stainless. Stainless does not need a coating for corrosion resistance, and inside a handguard the finish is never seen. A bright tube also makes it easy to check for bends and carbon.

Tube length is nominal per the mil-spec gas tube dimensions for each gas system. Gas block sold separately. Always confirm the gas system length listed on your barrel before ordering. Covered by the Faxon Lifetime Guarantee.