How Does a Rifle Trigger Work?

A rifle’s trigger is one of the most fundamental pieces of its construction. Not only does it allow you to fire the weapon, but it is also a key component of safety and accuracy. However, very few shooters understand how it works.

In Summary

Merriam-Webster defines a trigger as “a piece (such as a lever) connected with a catch or detent as a means of releasing it; especially: the part of the action moved by a finger to fire a gun”.

Let’s break this down in more detail for the gun enthusiast or one that wants to become an enthusiast.

The Breakdown of How a Rifle Trigger Works

In even the most basic of definitions the trigger is more than what you see projecting from the firearm, and upon which place your finger. This is more accurately referred to as the blade (see definitions below).

When discussing how a rifle trigger works you need to consider the entire trigger assembly. The exact components and how they function will vary based on the specific type of trigger used.
We will go more in-depth on the types of triggers and how they function later. For now, let’s review some basic definitions.

Trigger Definitions

Blade – the portion of the trigger that extends from the firearms and is engaged by the shooter’s finger.
Break – the point at which the trigger disengages (releases) the sear.
Creep – the amount of movement needed before trigger breaking.
Lock Time – the amount of time needed for the firearms to fire once sear is disengaged.
Reset – distance trigger must travel to reengage the sear after firing.
Sear – a mechanism that blocks or prevents the hammer or striker from contacting the firing pin.
Shoe – aftermarket device that attaches to the blade making it wider.

Stages

The majority of rifle triggers will fall into one of two categories: single-stage or two-stage. While there is very little difference in how these two types of triggers function, those small differences are very important.

 

Single Stage

This is the most basic trigger system on the market. However, do not confuse basic with cheap or undesirable. Many precision and hunting rifles utilize single-stage triggers, as does the M-16 / M-4.

With a single-stage trigger, the full weight of the trigger is held by the spring and sear. The result is little slack, or creep, meaning the rifle will fire as soon as enough pressure to overcome the initial trigger weight is applied.

The amount of pressure needed to fire a single-stage trigger is generally determined by the amount of sear engagement. The amount of energy needed is referred to as the trigger pull. A hunting rifle may have as little as 4 lbs. of trigger pull, while a precision rifle will have even less. You can use a universal pull gauge to check tension properly

The advantages of a single-stage trigger include slightly increased shot time with a quick reset. If you learned to shot with a shotgun or hunting rifle this is probably the trigger you are accustomed to so it will feel more comfortable as well.

Such light trigger pulls can lead to safety issues. If the firearm is dropped or mishandled it may have an unintended discharge. This is more common in bolt action rifles. For this reason most M-16 or AR- 15 designed included increased sear engagement resulting in trigger pulls between 5 1/2 to 8 1/2 lbs.

 

Two-Stage

The two-stage rifle trigger is similar to a double-action/single-action trigger in pistols. The users will initially experience take-up or travel, often confused with excessive creep. They will then encounter a heavier trigger pull and when this is overcome the rifle will fire.

With a two-stage trigger, the trigger pull is a combination of both the initial travel and heavier wall that needs to be overcome. For example, a trigger with a weight of 5 lbs. might have a 2 lb. pull during the initial phase and 3lb. pull to overcome the wall.

The advantages of a two-stage trigger include increased safety when dropped or bumped and the ability to stage your shoots. This makes it especially attractive in military rifles as the user can pull through the initial phase, ride the trigger until they are ready to shoot, and apply light pressure to send the round. For more information on a two-stage, we did a nice writeup on “what is A 2 Stage Trigger” here.

Set Triggers

Set triggers allow the users to select from a traditional full weight trigger pull or a reduced weight light trigger depending on the need at the time. This offers the benefits of a lighter pull without compromising safety and is most common on competition rifles.

The advantages of a set trigger are reduced disturbance of the rifle during the final shot and the ability to make faster shoots once a target is identified. This is especially useful when shooting for accuracy in an offhand stance. Some set triggers can also be adjusted to fit the individual shooter’s style and preference.

Disadvantages include up decreased safety and lack of accuracy from one shot to the next. Both issues can be overcome through a proper adjustment of the systems trigger pull.

There are two versions of the set trigger, single or double, which we will explore further below.

Single Set

This version consists of a single trigger or blade that can be fired in either of two manners. The first allows the trigger to function in a traditional manner – applied the required amount of pressure and the rifle fires. The second allows the shooter to set or stage the trigger via a mechanical action, either moving the trigger forward or activating a lever to the read of the trigger. This will then allow the firearm to function with a reduced trigger pull.

 

Double Set

The double set system achieves the same results as the single set except it utilizes two separate triggers rather than a trigger and lever. The first trigger sets the rifle and the second trigger fires it.

Depending on your specific firearm you will have either a double set, single-phase system, or a double set, double phase system. The double set, single-phase system can only be fired by utilizing both triggers. The double set, double phase system can be operated as a standard trigger if the set trigger is not used.

Variable Triggers

Variable triggers are a unique concept that allowed the users to experience select fire capability without the need for a selector switch. While this was a novel idea, and one rooted in a perceived need to eliminate unnecessary adjustments during a combat scenario, they have been all but abandoned.

The main reason variable triggers were abandoned was the complexity of the system itself. This made it difficult to maintain the firearm in the field and repairs often required a trained armorer. Users also found that under stress it was difficult to manipulate the triggers properly to achieve the desired rate of fire.

While there have been multiple experiments involving variable triggers the two most common were the double crescent and staged triggers.

 

Double-Crescent

In this version of a variable trigger, the rate of fire was controlled by where the trigger pressure was applied. Applying pressure to the upper portion of the blade allowed the firearm to fire in a semi-automatic mode. By holding pressure to the lower portion of the blade allowed the firearm to fire fully automatic.

 

Staged

With the staged, or progressive, version of the variable trigger rate of fire was determined by the amount of pressure applied to the blade. Light pressure allowed for single-shot use while heavier pressure allowed for fully automatic.

Both the double-crescent and staged triggers presented a fundamental problem – shooters under pressure or when panicked find it difficult to judge the amount of pressure they are applying to the trigger. The result is a shooter who unintentionally fires in fully automatic when a semi-automatic or single-shot mode was preferred. Since these variable trigger systems were typically used in a military rifle this became a critical flaw.

By better understanding how the various stock & aftermarket rifle triggers work you can choose the best trigger for your style of shooting as well as using the trigger to its full potential. This will help you understand the mechanics better and ultimately make you a better shot.