Fostech Echo AR-II Drop-In Binary Trigger

The Fostech Echo AR-II is a drop-in binary trigger for the AR-15. In Echo mode it fires one round when the trigger is pulled and a second when it is released, roughly doubling practical rate of fire. A three-position selector switches between Safe, Semi-Automatic, and Echo on the fly, so a shooter can drop back to standard semi-auto without removing the trigger. Moving the selector off Echo before releasing a pulled trigger cancels the release shot, which preserves a stop on a misidentified target.

The AR-II is a true drop-in cassette built on HIPERFIRE technology, and unlike older Fostech Echo designs it does not require Fostech's proprietary bolt carrier. It does, however, still require a full-auto (M16-cut) bolt carrier group to function: the AR-II dropped the proprietary-carrier requirement, not the full-auto-carrier requirement. The cassette itself installs into a standard mil-spec AR-15 lower with no gunsmithing and works with common 5.56/.223 builds. The unit ships with a stainless steel finish.

This is a range and competition trigger that exists to increase rate of fire; it is not appropriate for any duty or defensive use. Binary triggers are Title I firearm parts and carry no NFA paperwork at the federal level, but state restrictions vary widely and must be checked against current law before purchase. At a $479.99 MSRP the Echo AR-II is the most expensive AR-15 binary option on the market, and the Franklin Armory BFSIII AR-Essential undercuts it while delivering the same one-on-pull, one-on-release behavior.