I recently installed an HBI spring in a (self) polished FA binary trigger along with yetti wurks adjustable trigger shoe and I must say, it is simply amazing!
After some slight travel/reset adjustments with the shoe this thing is almost as fast as a forced reset trigger. With everything polished and the HBI spring it feels like the factory trigger with the HBI spring except travel and reset are almost zero, depending how you adjust the shoe.
The yetti adjustable shoe took a little filing to fit and was a pita to get adjusted but well worth the effort. The HBI spring was a simple drop in replacement.
At first I installed the stock FA trigger by it self and was simply awful. Yeah it was binary but it was stiifer than a priest at Sunday school and more grit than John Wayne but after, everything is buttery smooth and around a 5lb trigger pull.
