Workbook

LESSON 304: ADJUSTING THE TRIGGER

(Revised 01-15-01)

Giving directions on trigger adjustment is always scary. I'm waiting for somebody to disregard all cautions

and render the trigger unsafe, shoot somebody and try to make it my fault. Be careful. If you are not totally

confident - don't do it.

FAL triggers cannot be made into Olympic-grade target triggers, but they can be improved dramatically.

Metric guns require three hands (or a slave pin) for reassembly. Inch guns come with a slave-pin installed.

Metric guns have a spring and plunger between the sear and the trigger; inch guns have only a spring.

When the selector (change spindle) is placed in the fire position, it allows for movement of the trigger. The

hammer is held by the nose of the sear engaging in the sear notch (hammer bent). The hammer and the

hammer spring keep the sear to the rear so that the sear tail lies over the raised part of the trigger tail with the

sear spring compressed. When the trigger is pressed, the tail of the trigger pivots the tail of the sear upwards.

This disengages the nose of the sear allowing the hammer to fly forward and strike the firing pin under

pressure of the hammer spring. The sear, now free of the hammer notch, moves forward until it clears the

raised portion on the tail of the trigger. It can now rise up and bear against the underside of the hammer.

During the backward movement of the bolt carrier, the hammer is rotated rear and downward. When the bolt

carrier is to the rear, it is holding the hammer down. The sear is now in position behind the sear notch, but is

not engaged. As the bolt carrier returns forward, the sear engages the sear notch, but the tail of the sear sits

below the tail of the trigger. Only after the trigger is released will the sear tail rest on top of the trigger tail

and allow the cycle to repeat.

All three springs - the hammer spring, trigger return spring, and sear spring - are balanced. The hammer

spring must be heavy enough to override the firing pin spring and detonate even hard primers, yet the sear

spring has to override this tension to disengage the tail of the trigger. The trigger return spring needs to be

light enough for a comfortable, controllable trigger press, yet heavy enough to return the trigger forward and

disengage the sear. Modifying any one of these three springs will affect the others to some extent.

There are some subtle differences between FAL models. The Argentine and Brazilian trigger return spring

are usually heavier than the Belgium or Austrian version. The semi automatic Brazilian trigger return

plunger is equipped with a ring that serves to limit over-travel, which prevents full automatic fire .

Thumbhole stock L1A1s have a non-standard replacement trigger return spring that is simply horrid.

To effect a good trigger job, the nose and tail of the sear must be honed to a high polish. The edges must be

kept sharp and the original angles must be maintained. Often, on a parts kit, there will be a substantial burr

raised on the nose of the sear. I recommend a fine honing stone with the sear secured in a vise in such a

manner that the honing stone move parallel to the bench. This makes it easier to visualize and maintain the

correct angles. The notch in the tail of the trigger must also be honed.

Polish the sear and hammer pins to insure the sear and hammer move freely. Polishing the sear notch on the

hammer is difficult without a stone of the correct thickness and angle. Sixty degree triangle stones will

usually work. Changing the depth of the sear notch in the hammer adjusts creep. It is also a critical

adjustment and can result in “hammer follow,” a dangerous condition where the sear slips out of engagement

and the weapon doubles, or fires automatically without the benefit of a safety sear. The sharper the sear, the

more shallow this notch can safely be, but a slight rounding of the top of the sear makes for a smoother

release. Typically, factory new hammers have around a .030" notch. I do not recommend reducing this

below .020" and even that is only in conjunction with a perfect sear.