Faxon .875 Gas Block – 3 Screw Mount

The Faxon gas block screw mount is a rugged, precision-machined upgrade built for AR-10 shooters who want dependable gas delivery under a free-float rail. This three-screw .875 model is cut from high-strength steel and finished in corrosion-resistant QPQ, so it stands up to the heat and pressure that larger-caliber barrels generate. It is a simple part that makes a real difference in how consistently your rifle cycles.

What the Faxon gas block screw mount is and who it is for

This block is engineered to fit barrels with a .875-inch gas journal, the diameter commonly found on heavy-profile AR-10 barrels. If you are building a precision .308 or 6.5 Creedmoor rig on a bull barrel, this is the block sized for the job. Its low-profile design tucks neatly beneath most free-float handguards, making it a versatile choice across a range of build configurations.

Serious builders, gunsmiths, and anyone replacing a worn or oversized front assembly will appreciate how cleanly it integrates. The Faxon gas block screw mount keeps your gas system simple and repeatable.

Key features

• Compatible with .875-inch barrel gas journals on heavy-profile AR-10 barrels
• Machined from durable steel with a corrosion-resistant QPQ finish
• Low-profile design for maximum free-float handguard compatibility
• Secured with three steel set screws using a standard Allen key interface
• Measured dimensions of 1.024 inches wide, 1.00 inch deep, and 1.493 inches tall

Specifications and materials

The Faxon gas block screw mount is built from steel and treated with a QPQ process that hardens the surface while adding corrosion resistance and lubricity. That combination shrugs off the carbon and heat that build up right at the gas port on a hard-working AR-10. The result is a block that stays reliable long after the finish on lesser parts starts to fail.

Dimensionally, the block measures 1.024 inches in width, 1.00 inch in depth, and 1.493 inches in height, so you can verify handguard clearance before you order. A roll pin is not included, as this design clamps to the barrel with its three set screws rather than a pinned installation.

Heavy-profile AR-10 barrels run hotter and generate more pressure than a slim carbine barrel, which makes a stout gas block essential rather than optional. The QPQ treatment used here is prized for its combination of surface hardness and slickness, letting carbon wipe away instead of welding itself to the block. That matters on a large-format rifle that may run heavier suppressed loads. Getting the journal size right is critical, so measure your barrel before ordering to confirm the .875 fit.

Installation, care, and compatibility

Mounting is quick. Clean the .875 journal, slide the block into position, square it to the gas port, and tighten the three set screws evenly with an Allen key. A quality thread locker keeps everything torqued through sustained fire. Because it is low profile, this Faxon gas block screw mount clears the vast majority of AR-10 free-float rails on the market.

Maintenance is minimal. Wipe it down during routine cleaning and recheck the set screws now and then for consistent tension. Pair it with a rifle-length gas tube sized for your build and you have a complete gas front end. Browse our wider parts and upgrades selection for the tubes, pins, and rails that finish the job, and lean on Faxon quality for the parts that matter most.

Because it clamps rather than pins, this block is easy to remove and reinstall if you ever rebarrel or reconfigure your gas system, which is a real advantage on a rifle you plan to evolve over time. Builders often dimple the barrel beneath the set screws for extra security against movement under recoil. On a precision AR-10, consistent gas timing is part of the accuracy equation, and a solid, correctly sized block is where that consistency starts. It is a small investment that protects a big one.

For an AR-10 that needs a heavy-barrel gas block you can trust, the Faxon gas block screw mount is a smart, affordable pick. Ships direct to your door, no FFL required.