WHAT DOES FRT TRIGGER MEAN?

I made an effort to acquire one for an acquaintance, but They can be by no means in inventory.  If I am unable to only click and buy, I'm not gonna hassle. I have also purchased an adjustable fuel block to the carbine size and plan on opening up the barrel gasoline port in smaller increments if The brand new BCG will not solve this.  I've a #41-