Two-stage competition triggers are designed to give AR -15 shooters a trigger pull with separate tensions, the first part of the pull requiring a slightly greater amount of pressure than the second. Two-stage triggers are particularly useful for precision shooting. Bushmaster two-stage triggers can be adjusted by using a .035 inch Allen wrench and a pair of needle-nose pliers. Before working on your rifle, remove the magazine and make sure the rifle is not loaded.
Separate the rifle's lower receiver from the upper receiver and set the upper receiver aside. The upper receiver consists of the barrel and bolt assembly and the lower receiver is the half of the rifle made up of the trigger assembly, magazine well and stock. They can be separated by pressing the retention pins--located behind the selector switch and in front of the magazine well--through the body of the rifle.
Use your finger to pull the hammer back until it cocks--locks into position--and place the safety on.
Loosen the set screw on the spring plunger--located on the left of the safety selector switch--with the Allen wrench. Place the safety selector on the "fire" position.
Use the needle-nose pliers to gently turn the spring plunger clockwise until you feel the tension reduce to the second stage. Place the safety selector switch to "safe" and tighten the set screw on the spring plunger.
Now that the trigger has been adjusted, rejoin the upper and lower receivers.