Trigger Terminology and Causes/Fixes

[1894]

I have been shooting for a little while now and have noticed that I'm better with some guns than others. The triggers are all different. Some I love, some I hate. I shoot more accurately with the guns that have triggers I love (duh). The problem is that I have no idea how to discuss why I love/hate the ones I do. I know what I like but, I have no clue what terms to use to describe why. As such, I don't know what/how to fix what I'm doing wrong. I mean, I think I know what over travel is, but I have no idea what effect it has on my shooting.

My first gun was a full size HK USP. I decided on it a decade ago because the internet told me to. At 7 yards I can hit a paper plate. Probably. Later, I acquired a 2 1/4" SP101 in .357. My first 50 rounds left my hand bleeding from all the sharp edges. Tinkerer that I am, I took it apart and put a file to the frame and 1000 grit sand paper to the internals (I finished with 2000 grit). I love this gun now! The shots go where I want them at 20 yards(3-4 inch groups). Yeah, Bubba got lucky as all get out. I tried the same with a GP100 (internals only) with less spectacular results (it's better than it was but not as good as the SP101). But I don't know the terminology to explain the difference.

Is there a resource that defines all the terms used to describe different trigger pulls and their practical effects and causes/fixes? Or, would any of you please provide one?

 

[WNTFW]

Look up
Pre Travel or Take UP or Creep
Trigger Pull or Pull Weight
Trigger Break
Over Travel


Negative Sear Engagement
Neutral Sear Engagement
Positive Sear Engagement

1 thing to watch is removing the hardening from a part.


Past that I would just give you a warning that you could make a trigger worse or unsafe. I know you will probably get some lectures about working on the trigger yourself. I give you the credit that you will proceed with safety in mind.

 

[1894]

Perhaps I should've been more clear. I'm not looking for how to perform a trigger job. I'm looking for how to talk about why I want one to a gunsmith. And, what I should be able to expect from his work.

 

[MistWolf]

From a post I made on another site-
About "good triggers". A good trigger is one that is reliable and predictable. Reliability means it fires every time and predictable means it performs and feels the same way every time it's pressed. Smooth is what makes a good trigger (reliable & predictable) better. A good trigger is still a good trigger and doesn't always need to be replaced with a better one.

A trigger that's reliable but with an unpredictable pull is merely acceptable. An unreliable trigger is a poor one and should be replaced.

A better trigger will not make one a better shooter, nor is it a crutch. It's just better and makes it easier for novice and expert alike to shoot their rifle well. Easier enough to justify upgrading a good trigger? That call is up to the individual and the only way to know is to shoot

Some terminology-
CREEP Creep is how much travel the trigger has, under full weight, before it breaks. It is the movement of the sears. No creep is preferred for precise shot placement as there is less chance of disturbing the aim before the shot breaks as the time from when the trigger is pressed to the time the shot breaks is less.
OVER TRAVEL Over travel is the distance the trigger moves after it breaks. Less over travel is desirable as the continuing motion of the trigger can cause the weapon to move while the bullet is still traveling down the barrel.
SLACK This is the amount of motion the trigger goes through before engaging the sear. Taking up the slack does not move the sear or perform any other function. It's simply wasted motion.
SINGLE STAGE A single stage trigger is one that has no travel before engaging the sear to break the shot. A single stage trigger can have slack.
TWO STAGE A two stage trigger is one that has travel before engaging the sear. It differs from slack as it's part of the trigger design. Two stage triggers are generally used in infantry rifles to prevent discharges from rough handling on the battlefield and to provide the soldier a tactile warning that the trigger is being pressed. Two stage triggers often use a physical block that will prevent the sear from releasing the hammer/striker if the rifle experiences a hard jar. The first stage disengages this block before engaging the sear, which is the second stage. NOTE: The standard AR/M4/M16 trigger is a single stage.
PREDICTABILITY A good trigger has the same feel and the same break with every press. A trigger with a heavy, long pull that feels the same way every time is preferable to a light, crisp trigger that never feels the same way twice.
GRITTY/SMOOTH This describes how the trigger feels during it's travel. Smooth is better than gritty (or rough) as it's more predictable.
LOCK TIME The time from when the sear breaks until the hammer/striker hits the primer, or the time the sear breaks until the shot is fired. Shorter is better for precise shot placement. A hammer/striker with more mass is slower but gives a more reliable and consistent ignition.
TRAVEL The amount of motion the trigger bow has during the operation of the trigger.
PULL/PULL WEIGHT How much weight is needed to operate the trigger.
TRIGGER BOW The part of the trigger the finger engages.
SINGLE ACTION The only action a single action trigger performs when pressed is releasing the sear.
DOUBLE ACTION During the trigger press, a double action performs two actions: It cocks the hammer/striker and as the travel continues, releases it to fire the weapon. Double actions need longer, heavier pulls than single actions.
STACKING/WEIGHT STACKING Some double actions have the same pull weight throughout their travel. They are non-stacking. Some have an increase in pull weight, peaking right before the release point. This is known as stacking. Some prefer a non-stacking trigger as they find it easier to stroke through the pull until the shot breaks. Some like a stacking trigger as they prefer to stop the trigger press right before it breaks to settle sight alignment before firing.

When tuning triggers, it's best to not go for the lightest, crispest pull possible. The lighter, crisper the trigger, the more trouble it will have with reliability. A light trigger is best left for experienced shooters. Crisp, smooth triggers will feel lighter than they really are. It's easier (and safer) to get a crisp break with a 5 lbs trigger pull than a 2 lbs pull. Don't go any lighter than 5-4.5 lbs on a single action or about 10 lbs on a double action until you gain more experience

 

[Standing Wolf]

From one wolf to another: thank you, MistWolf!

 

[9mmepiphany]

When I started shooting, the preferred trigger break was a crisp one...often described as like a glass rod breaking, so sudden and sharp. This is what you will often hear related to folks who sing the praises of the 1911 trigger. This preference comes from the world of Bullseye shooting where accuracy outweighed everything else.

For many years, these glass rod breaking triggers also ruled Action Handgun competition...where there is a balance of accuracy and speed of shooting. In the past few years, there seems to have been a move away from these triggers are the higher levels of action shooting.

What they have been moving to is often referred to as a Rolling Break...where there is more creep built into the trigger at let-off. This isn't a safety feature, as it might be for a defensive handgun. It is to allow the shooter to stand on the trigger, after resetting it while in recoil, to facilitate a faster and more accurate followup shot.

When talking to a gunsmith about tuning a trigger I've found that common mistakes from new shooters are asking for triggers that are
1. too light (not as much of a positive as people think)
2. lack overtravel (affects reliability)
3. reduce slack (not always practical depending on trigger design)
4. reduce reset distance (most can't use it effectively)

IMO the key a good trigger, with reliability as a given, is smoothness and consistency...what my goal is, is to have any grittiness removed; as well as uneven travel

 

[1894]

Thank you Mistwolf.

It seems (I think) that over travel is my problem w/ the GP. Not sure what it is w/ the HK. Maybe it's just to darn big for my hands. But, now that I know what the terms mean, I can at least begin the conversation to find a fix.

9mm, Thanks for the caution. I'm not looking to reduce the weight of the triggers. What I want is smooth and consistent with as little over travel as reliability will allow.

 

[9mmepiphany]

Just to give you an example of overtravel reduction. The S&W M14, M16 and M17 Target Masterpiece series used to come with an adjustable trigger stop built into the rear of the trigger guard. It was a metal piece that could be pivoted out to meet the back of the trigger just as it released the hammer. The problem was that the point is different for the DA and SA releases.

It is actually quite easy to address on a revolver...all you need to do is install a trigger stop. First you'll have to decide it you want to shot in DA or SA. You can then approach it from either of two directions...the trigger facing rearward or the back of the trigger guard facing forward.

The quick and dirty way is by gluing a piece of rubber (like an eraser) to the surface. The more professional way is by drilling a hole and inserting a screw. Then you just adjust to the correct lenght