Instructions For Installing Drop In AR-15 and AR-10 Trigger Groups
Updated
If installing in a receiver that already has a trigger and hammer installed, remove the trigger pin and hammer pin and remove the trigger and hammer as well as the grip, safety selector and detent. New receivers, install the drop in trigger before mounting the grip.
Insert the trigger pack into the fire control compartment.
Insert the hammer and trigger pins. Anti-walk type pins work much better, as standard pins can drop out.
Towards the rear of the trigger cassette you will see two small set screws. With the trigger and hammer pins in place, turn those set screws down to raise the trigger to the point that there is pressure created on the trigger and hammer pins which will hold them in place. This step is VERY important and will take care of the slight dimensional differences between lower receivers.
Install the retainers on the anti-walk pins
Insert the safety selector switch. The hammer needs to be in the cocked position. Take care as it is inserted to not push the selector into the back extension of the trigger. Replace the safety detent, spring and grip.
At this point you can test the trigger pull and reset.