The Fostech Echo AR-II is the second generation of Fostech’s flagship binary trigger system for the AR-15 platform, and it stands as one of the most technically sophisticated aftermarket trigger designs available for the black rifle. The Echo AR-II is not a Forced Reset Trigger — it is a binary trigger, meaning it fires one round when the trigger is pressed and a second round when the trigger is released, effectively doubling the theoretical rate of fire of a standard semi-automatic trigger through a different and independently developed mechanical approach.
Fostech’s approach to binary fire differs from competitors in an important functional respect: the Echo AR-II incorporates a selector-controlled cancel feature that allows the shooter to switch from binary mode back to standard semi-auto mode and absorb the chambered reset shot safely. This is the feature that has made the Echo AR-II the preferred binary trigger among instructors and professionals who need the option to de-select binary mode without firing the reset round — a scenario that can arise at the range when a cease-fire is called mid-string of fire.
The Echo AR-II trigger group consists of a fully machined trigger, hammer, disconnector, and binary sear, all manufactured from tool steel with heat treatment specs that bring critical surfaces to 58-60 HRC. The trigger has an adjustable reset — using the included hex key, shooters can tune the reset distance to their personal preference. The single-stage trigger pull weight in standard semi mode is approximately 4.5 pounds with minimal take-up and a clean break.
Installation compatibility covers mil-spec AR-15 lower receivers in all major calibers: 5.56, .223 Wylde, .300 BLK, .450 Bushmaster, and others using the standard AR-15 BCG. The Echo AR-II is not recommended for use with pistol-caliber carbine lowers or non-standard pin spacing. Installation requires a three-position safety selector (also available from Fostech) if binary mode selection is desired — binary mode is only accessible through the dedicated selector position.
The Echo AR-II ships in Fostech’s retail packaging with trigger assembly, springs, three-position selector, installation instructions, and a product registration card. The trigger carries a limited lifetime warranty to the original purchaser against manufacturing defects in materials and workmanship.
