The Ergo 4821 .750 Low Profile Gas Block is designed to fit under the Ergo Modular and SuperLite™ Rail System, as well as most other manufacturer’s free float handguards.


  • CNC machined 4140 chromoly steel
  • Black Nitride/Melonite Quench Polish Quench (QPQ) finish
  • Chamfered edge, slip on fit
  • Weighs 2oz
  • Fits under most free float handguards
  • USA made steel & Machined in the USA
  • Internal Diameter 0.750
  • Includes (2) set screws for a secure attachment
  • Accepts standard gas tube roll-pins (roll‑pin NOT included)


**It is recommended that the barrel be dimpled for the set screws to achieve the most robust barrel to gas block fit**

  1. Loosen the set screws and slide the gas block assembly onto the barrel with the hole for the gas tube facing the receiver.
  2. If using a standard handguard with the metal handguard end-cap, slide the gas block all the way on until it hits the end-cap. If you are using a free-float handguard, do not push the gas block against the shoulder of the barrel. You must leave a .025”-.035” gap between the shoulder of the barrel and the gas block for proper alignment of the gas port in the barrel and gas block.
  3. Be certain that the top of the gas block is in alignment with the gas tube hole timing at the 12 o’clock position in relation to the barrel and receiver. A suggested way to do this is to look down the barrel and receiver at the gas block, checking for alignment.
  4. When the desired alignment is achieved, lightly tighten down one of the set screws to maintain timing during final set screw installation.
  5. Removed the other set screw and apply a high temperature thread locking compound to the threads only. Re-install the set screw with the thread locking compound into the gas block and tighten to 30-32 in/lbs using a 3/32 hex key.
  6. Remove the other set screw, apply thread locking compound, re-install in to gas block, and tighten to 30-32in/lbs using a 3/32 hex key.
  7. Check gas block alignment and the set screws torque one final time.
  8. Install the gas tube into the receiver/barrel/gas block assembly. Ensure that the hole for the gas port is facing towards the barrel/gas port.
  9. Align roll pin hole in the gas tube with the roll pin hole in the gas block.
  10. Install the roll pin into the gas block.

**The gas tube can be installed into the gas block before the installation of the gas block onto the barrel**

Additional information

Weight 0.12 lbs
Dimensions 20 × 1 × 5 in


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