The Riflespeed adjustable gas block .875 4.8-inch is a tool-free gas control for AR-15 and AR-10 pattern rifles whose barrels carry a .875-inch gas-block journal. Riflespeed built it around a numbered control knob with tactile click detents, so a setting can be changed in seconds and returned to later. The 4.8-inch assembly is one of the longer .875 models and is meant to sit under an extended handguard. It lets a builder tune gas flow for different ammunition, suppressor use or changing conditions without tools or a trip to the bench. For a rifle that runs both suppressed and unsuppressed, a single adjustment replaces swapping parts.

Key Specifications

• The gas-block journal fit is .875 inch, so this model is for barrels with that journal diameter and not the .625 or .750 versions.
• The assembly length is 4.8 inches, which suits a long extended handguard where the control knob has to reach the front of the rail.
• Adjustment is tool-free through a numbered control knob with tactile click detents, which makes each setting visible and repeatable.
• A rotation stop limits how far the knob turns, which prevents the block from coming apart by accident while it is being adjusted.

Frequently Asked Questions

Which cartridges does it work with? Riflespeed lists .223 Remington/5.56x45mm, 300 AAC Blackout, .308 Winchester/7.62 NATO, 6.8 SPC and 6.5 Grendel, along with other cartridges when the modular plunger system is set up correctly.

What gas tube does it need? It is designed for straight gas tubes. Riflespeed-brand straight gas tubes or equivalent straight gas tubes are required, and the tube is sold separately from the gas block.

Buy the Riflespeed Adjustable Gas Block, .875-Inch Journal, 4.8-Inch Gas Control

Gas tuning is one of the few upgrades that changes how an AR feels at the shoulder, and a block you can adjust without tools makes that tuning practical at the range. This 4.8-inch .875 model is the choice for builds with a long handguard and a .875-inch journal. Order it from our Lubbock, Texas gun shop for fast, direct shipping, and browse more AR-15 accessories and parts while you are here.