Fostech – ECHO Sport Trigger for AR-15 Platform

As with all binary triggers, you will need to run a full-auto bolt carrier group (BCG) in order for your AR15 to run properly.

The Echo Trigger has three positions:

  • Safe Mode – The firearm will not fire.
  • Semi-Auto Mode – Like standard triggers, the firearm fires will the trigger is pulled.
  • Echo Mode – The firearm fires when the trigger is pulled and when the trigger is released which makes for a rapid rate of fire.

As of March 2022, the Bureau of Alcohol, Tobacco, and Firearms issued their opinion on binary triggers allowing for their legality as they do not make firearms fully automatic.

We cannot ship binary triggers to the following states because they have been banned per State Law: California, Colorado, Connecticut, Delaware, Florida, Hawaii, Idaho, Illinois, Iowa, Maryland, New Jersey, New York, Rhode Island, Virginia, and Washington.


7 in stock

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SKU: ECHO-4140 Categories: , Tag:

Specifications, description, Reviews & Questions

.4 lbs
9.5 × 5.6 × 1.2 in

About Fostech

Fostech is a family owned company based in Southern Indiana. Fostech Inc makes AR-15’s, 12 Gauge Shotguns in AR style, binary triggers for both the AR and AK platforms, as well as many AR parts. All Fostech products are proudly made in the United States.

The Echo AR-II Trigger is a groundbreaking drop-in design that is approved by the ATF. The Echo AR-II trigger does not come with a bolt carrier. 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

Questions and answers of the customers

    Does your echo 4140 sport trigger for AR-15s fit for a Smith & Wesson m&p sport 2 rifle?
  1. 0 votes
    Q Does your echo 4140 sport trigger for AR-15s fit for a Smith & Wesson m&p sport 2 rifle? answer now
    A Does your first tech echo sport trigger for AR-15s fit in a Smith & Wesson m&p 15 work to rifle?