There are many common question about triggers such as what is the difference between a single and two stage trigger? What is Pre-Travel? What is Take-Up? What is Trigger Creep? Choosing the right trigger for you brings up many questions so this guide will try to answer those questions.

First an overview of the different phases of the trigger activation:
  • Pre-Travel - The Pre-Travel is made up of three phases itself:
    • Trigger Take-Up
    • Trigger Wall
    • Trigger Creep
  • Break (or release)
  • Over-Travel
  • Reset
What is Pre-Travel? The Pre-Travel has three phases itself which are the Trigger Take-Up (often called "Slack"), the Wall and Trigger Creep.

What is Trigger Take-Up? Trigger Take-Up (or sometimes called "Slack") is defined as any rearward movement of the trigger that does NOT cause the sear to move and does NOT engage the hammer spring or mainspring. There is usually very little resistance in this phase. A good single stage trigger won't have any perceivable take-up but in a 2nd stage trigger the first stage would be the take-up.

What is the Trigger Wall? The Wall is defined as where the sear starts to move or the mainspring is engaged. This is where the main resistance in the trigger will be felt and lasts until "the break" or "release" of the hammer or striker (on pistols that have strikers instead of hammers). In a single stage trigger the force measured in pounds to force the trigger to break is first encountered at this point. In a Two Stage trigger this would be the second stage.

What is Trigger Creep? The Creep is the rearward movement of the trigger after the wall that causes the mainspring to compress and the sear to move. At the end of the creep comes the break (or release) and the measurement of force would end. Any resistance in the creep that causes the sear to stop and start movement is called "steps" which is what feels like "grit". All triggers have "creep", but with a good quality trigger you won't feel much if any perceivable creep as it will be so smooth and short that it really feels like a wall and the break.

What is the Trigger Break? The Trigger Break (also called the "Release") is when the sear releases the hammer or striker. Once the hammer hits the firing pin and the pin (or striker) hits the primer the gun will fire. When a trigger is said to have a "crisp" or "clean" break it means there was either very little or no perceivable creep.

What is Trigger Over-Travel? Over-travel is any rearward movement of the trigger following the Beak. Usually Over-Travel has little resistance but the trigger is still moving even though the hammer (or striker) has already been released. Some triggers have adjustable Over-Travel and other triggers are pre-set with a "trigger" stop so there is very little Over-Travel. Sometimes that trigger stop is the receiver itself, other times it's an adjustable screw or something else that stops the trigger. You don't want much overtravel as that movement of the trigger could cause other movement in the firearm which could throw off your accuracy.

What is Trigger Reset? Trigger Reset is the forward movement of the trigger pushed by the trigger spring to the point that the trigger resets where the sear can be engaged again. This also takes in to account the cycling action of a semi-auto.

What is the difference between a single and two stage trigger? Single stage triggers have one consistent pull weight throughout the pull of the trigger. For example if a trigger says it has a 4.5lb pull weight then the pull weight will stay at 4.5lbs. Two stage triggers have two different stages, usually with different pull weights. Typically a two stage trigger will have a lighter first stage take up of 2lbs and then a wall that requires a bit more force to make the trigger break.

What kind of trigger is the standard AR-15 trigger? The Mil-Spec AR-15 trigger is a single stage trigger with a pull weight from 5.5lbs to 9.5lbs. Some Mil-Spec triggers have a lot more pull weight than others. Most of them have a lot of take up, and some have very gritty creep. Some Mil-Spec triggers are fairly smooth and overall not bad but all of them leave a lot of room for improvement. 

Should I use a single or two stage trigger in an AR-15? Ultimately that is up to you but it can be guided by what is this AR-15 going to be used for? If it is a self defense, home defense or fighting carbine a single stage trigger would be best. Two stage triggers are best in a precision rifle meant for longer range shooting and even then it is user preference.

What trigger pull weight should I get for an AR-15? This depends on what the rifle is used for as well as user preference. Usually 3lbs is the lightest most people want to go in an AR-15 but there are a few 2.5lb triggers out there. If you have a self or home defense carbine you might want to stick to a 3.5-5lb trigger. If it is a precision rifle a slightly lighter trigger pull might be desired.

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