Two Stage Trigger vs Single Stage Trigger

Wisconsin Trigger Company - Two Stage Trigger vs Single Stage Trigger


By Ron Albanese, owner of the Wisconsin Trigger Company

In part 2 of M-K Trigger Talk (Read Part 1) we will cover how a two stage trigger and a single stage trigger differ and the strength and weaknesses of each style. I will also indicate what to look for when you’re shopping for a new trigger.

2 Stage M-K X Trigger with the Hammer in Place
2 Stage M-K X Trigger with the Hammer in Place

We will start with a 2 stage trigger. A 2 stage trigger is just that, it has 2 stages. It has a first and a second stage. The first stage is the first part of the trigger pull. As you start to pull back on the trigger, the Hammer’s Trigger Hook and the Trigger’s Hammer Hook slide over each other, with the hammer staying as still as we can keep it and the trigger moving. As the trigger moves, the two hooks get closer to the point that they will no longer overlap and the hammer will be released. Before that point, just a few thousands of an inch from separation, the disconnector will start to hold back the hammer. This position is known as The Wall. This is the point that first stage ends and second stage starts. The second stage is from the point called the wall until the hammer is actually released. To get to the end of second stage you need to get the hammer and trigger to separate. You will need to overcome the pressure of the second stage spring, at which time the trigger will go past the wall, removing all the overlap and releasing the hammer. That is the end of second stage.

The main benefit to using a 2 stage trigger is increased accuracy. With the trigger stopping at the wall, the shooter knows to the thousandth of an inch when the hammer will be released. This accounts for the remarkable increase in accuracy over a single stage trigger. The only draw back to a 2 stage trigger is they tend to have a slightly longer pull and a longer reset compared to a single stage trigger. This longer pull makes them a bit slower in something like a 3 gun match. However, in a non speed shooting event the lack of speed is no disadvantage to the shooter. It comes down to trading off some speed for a much greater amount of accuracy.

Now let’s look at the single stage trigger. As you can guess by the name, the single stage trigger has just 1 stage. There is no second stage so there is no wall. The pull is just one motion. When the shooter pulls the trigger, the hooks on the hammer and on the trigger move and separate the same as a 2 stage trigger. When they separate the hammer is released. Pretty simple.

Single Stage BCM Trigger
Single Stage BCM Trigger. G.I. Style. This is one of the better single stage triggers

The advantage of a single stage trigger over a 2 stage trigger is speed of trigger pull. A single stage trigger can be made to have a very short pull length and a short reset. The disadvantage of the single stage trigger is a lack of a consistent release point. The shooter has no way of knowing just when the hammer will be released and this has a large effect on accuracy.

Now that you know the basics of a 2 stage trigger and a single stage trigger, we come to the part where I do the sales pitch and tell you why the Wisconsin Trigger Company M-K triggers are far superior to the other AR-15 trigger on the market. I will also explain what you should be feeling in your trigger finger and how properly machined high-end 2 stage match style triggers works. I hope this will give you some insight as to what you should look for in a 2 stage trigger when you start your next AR-15 build or when you look to upgrade your favorite rifle.

The first thing to look for (and one of the easiest features to spot) is an adjustable disconnector. This is the heart of a match trigger. Triggers that are not adjustable will have trigger creep built in to them. They have to have it. Trigger creep is when the wall is reached too early in the travel of the trigger rearward. If the wall is hit too soon, the hook overlap will be too great. This will cause the trigger to need to be pulled farther past the wall before the hammer is released. That distance is the creep.

As the Trigger is pulled the two hooks will separate
As the Trigger is pulled the two hooks will separate
AN M-K X Trigger with the Hooks at the Wall. The start of second stage.

One thing is for sure. All AR-15 lower receivers are NOT the same. The pin holes, the detentes, the safety selector hole. From one to the next they are all a bit different. A thousandth here and thousandth there. You can’t even say it’s high dollar versus low dollar. No two are the same. If you build a trigger that has the wall 100% perfect for receiver A, then you put it in to receiver B, you will find the wall is way off. If it’s off to the early side the hooks will have too far to travel after the wall and you will get trigger creep. That’s not good but at least you have a working 2 stage trigger. What happens if it’s off to the late side? The two hooks will separate before the wall is reached and you have a single stage trigger. That’s not good and it’s not safe. The rifle will fire before the shooter wants it to. So the answer is to err on the side of safety and have the wall come in a little early. You may not have the best trigger, but at least you can say it’s a 2 stage trigger and it’s safer then the alternative. The only way around is to make the disconnector adjustable. You can make up all the difference and inconsistency in the lower receiver by setting the disconnector timing for each individual lower receiver.

All M-K triggers have an adjustable disconnector. This means you determine the timing of the wall. If done properly you will have zero trigger creep. You use the disconnector adjusting screw to change the timing to match your receiver. Even with an economy priced lower receiver you will have the perfect wall position. That gives you a predictable and consistent crisp release every time you pull the trigger. The creep goes down and the scores go up.

Continuing with the disconnector, we turn to the automotive world for the next term. Divorced and Married just like a transfer case except we are talking about a disconnector. A Divorced disconnector is a disconnector turning on its own pin. A Married disconnector is a disconnector that mounts on the same pin as the trigger. All M-K triggers have a divorced disconnector. This give them an advantage in geometry and helps give them a superior release. Geometry plays as much a part in getting you the perfect release as precision machining does.

These are some of the things that go in to giving the shooter the finest most crisp snap of a hammer release he can get. For more information on how to set the disconnector on an M-K trigger, our instruction manuals are posted on the Wisconsin Trigger website. Please look them over. The M-K triggers are not the only adjustable and divorced AR-15 trigger, but we were the first.

In part 3 we will cover Grit and start on Overtravel.

About the author

Ron Albanese is the owner of The Wisconsin Trigger Company. Ron has over 30 years experience in the firearms industry. His company produces the M-K series of AR-15 triggers. Ron is proud to offer these triggers. From the first 2 stage trigger ever fit into an AR-15, the M-K II in the late 1980’s to the latest world record setting and National Match winning M-K X trigger, the M-K series triggers are an outstanding choice for AR-15s.