Fostech ECHO AR II Trigger



UPC: 639266300021 SKU: 4150 Categories: , , Tag:

The Echo Trigger allows the shooter to select from 3 different settings:

  • Safe Mode: Firearm will not fire.
  • Semi-Automatic Mode: Firearm fires when the trigger is pulled.
  • Echo Mode: Firearm fires when the trigger is pulled and also when the trigger is released.

The Echo Trigger is designed with safety being the utmost priority. When the shooter is in the Echo Mode and depresses the trigger one round is fired, if the target moves, the shooter can move the selector to the safe position and a second-round will not fire upon release.

You will need a full auto bolt carrier in your firearm for the Echo AR-II to function. The Echo AR-II is designed to function in the AR-15 Platform. If you have any questions in regards to if you have a full-auto carrier, please visit

Full Auto Bolt Carrier Options from Fostech


  • Mil-spec AR15 Lower Reciever
  • Ensure the lower does not have a sear block or other non-mil-spec attributes
  • Must have matching buffer assembly (Both carbine and rifle length will work, but must not be mismatched.
  • Ensure buffer is not solid, sand or captured spring.
  • Must have full-auto bolt M16 cut.


  • H buffer – Ensure that when you shake the buffer, it rattles. Occasionally an H2 Buffer may be required for the Firearm to fire properly.
  • Some lower receivers have a sear-block or wall; the sear wall will prevent the trigger from functioning as designed.  The wall of extra material causes the trigger lock to remain compressed forward and can cause improper fitment of the selector switches.
  • Large trigger pin lower receivers are not compatible. The Echo ARII Trigger uses standard trigger pins. You are welcome to use anti-walk pins if you would like.
  • Most Carbon Fiber or Polymer Lowers have extra supports. Extra supports that get in the way of the trigger pack are not compatible.
  • Some lower receivers may use a set screw, the set screw will need to be removed, as it impedes on the trigger causing improper function.
  • For further questions, feel free to contact FosTecH Echo Department, technical assistance. 812-445-4028 ext. 104.


  • PATENTED Design that gained ATF Approval (Patent # US 8,820,211 B1)
  • PATENTED Technology licensed through Franklin Armory inside the Echo AR-II Trigger, including U.S. Pat. Nos. 9,952,012 and 9,952,013.
  • Technology licensed through HIPERFIRE inside the Echo Trigger
  • Light, clean, and crisp pull in Semi-Automatic Mode
  • The Echo Trigger is packed full of cutting edge technology
  • Reliable function in Echo Mode


*We are unable to ship the Echo Triggers to CA, CT, DC, FL, HI, IA, MD, NJ, NY, RI, and WA