Sunday, June 17, 2012

AR-15 Triggers

To many a trigger is just a trigger and it's not for indifference to the topic but simply there aren't a lot of people that understand how a trigger works. On the high level, you pull the bang switch and it goes either boom or click and it's a combination of alchemy and black magic to make that happen and I am here today to discuss what that alchemy and black magic looks like inside of an AR-15.

Many of us were introduced to a trigger for the first time on Duck Hunt, and I don't mean the actual sport of hunting but the video game that is Duck Hunt. We slapped at that trigger for endless hours and some of us evolved our trigger fingers to air-soft, paintball, newer FPS video games, and firearms. Even after those countless hours on various triggers and even refining how one pulls on that trigger, the function remains a mystery to most. Much like driving, one does not need to understand how a steering wheel works in order to operate one.

F$%& you dog, f!@# you.

I decided to discuss good trigger habits first as it directly relates to how triggers are designed the way they are and why you should learn to pull them properly. When you pull a trigger on a firearm, there is a section in the beginning of the trigger pull that moves easily and that is called take up. The take up is there as a margin of safety to that firearm and prevent accidental discharge. After the trigger movement to the rear completes you should hold the trigger there and that is called follow through and once you learn follow through, next thing to learn is reset. Reset is when you start to release the trigger after the follow through and release it slowly until you can train your self to feel or hear a 'click' of the trigger as you slowly release it and the trigger is reset for another shot without the need to let go of the trigger completely. Training for reset is crucial to rapid fire with accuracy and with training you will develop muscle memory of where that reset is on a given trigger in a specific firearm.

Single stage G.I. type hammer (L.) and trigger+disconnector (R.) assembly from '73 Colt SP-1

Disconnector disassembled from trigger to show how it fits

Trigger and hammer contact surfaces highlighted in red box

Trigger group mounted to the outside of an AR lower to demonstrate how it fits inside lower, red box highlights hammer and trigger mating surfaces in the ready to fire position.

Red box highlighting where disconnector and hammer connect during follow through. This is what lets off and makes the click when the hammer and trigger re-engage to be ready to fire again. You can see in an earlier picture that the disconnector sits on a spring and held captive by the trigger pin which becomes a pivot, the disconnector can move back and down ~1/8th of an inch to give the hammer clearance than spring back to engage it at follow through.

With AR-15 triggers you will come across a broad variety of triggers and the first thing that many of you will consider is to use either a single stage or 2-stage trigger. The difference between the two is that the two stage has two pull weights that equal one larger pull weight. Example of comparison is that a stock G.I. trigger in an AR-15 is a single stage 6.5 lbs trigger where you must overcome the entirety of the pull weight at once versus a two stage trigger at 4.5 lbs typically has a first stage of 2.5 lbs and and a second stage at 2 lbs more of resistance to overcome before the trigger breaks. A typical 2-stage trigger in reality feels like it has a longer take up and a very short break at the end. While on this topic in regard to 2-stage triggers, there is a phenomenon called stacking which is not a desirable feature in a 2-stage trigger. Stacking is when you feel a 'wall' in the second stage where the pull weights 'stack' to the overall trigger pull weight and creates a jerky feeling trigger. You want to have a smooth trigger pull across both stages as any interruption to the pull can deviate a shot in an untrained hand and even in a trained one.

Once decided on a single stage or two stage trigger, next comes well; which one? There are a variety of triggers on the market from those that aren't going to offer anything better than what you already may have to making it feel like light and day. I shoot the hell out of my carbine and what I want is a trigger that is not only smooth but durable and it is with this in mind that I will be going over some triggers available on the market today. There seems to be a misunderstanding between a smooth trigger and light pull weight, where an easily pulled trigger with little resistance has been equated to a smooth trigger pull but that statement simply isn't true. Smoothness should not be correlated to weight and if it is, you have a very gritty trigger. A gritty trigger is a trigger where the wear surfaces (those that come in contact metal to metal) has not been polished and honed to ease the metal to metal transition. Once grit gets cleaned up, a heavy G.I. trigger can still feel smooth with a predictable break in the trigger every time.

I am going to start with my recently favorite 'value' trigger. It is a single stage service trigger with nothing really special as far as the trigger and hammer are concerned, what is interesting is an additional metal plating process and which company it shares space with. The trigger I am talking about is the ALG Defense Combat Trigger or ACT for short. The trigger is nothing special as I mentioned, a 5.5 lbs. pull duty trigger but the finish on the surface is Nickel Boron, which increases surface toughness as well as having a self lubricating property to it which is favorable to any firearm component that sees a lot of wear from surface to surface contact. The second part of who ALG shares space with...... Geissele Automatics. I little further digging and I have discovered that ALG is Bill Geissele's wife's company, seems triggers are a family tradition for the Geissele's.

Speaking of Geissele Automatics, the trigger I plan to install on my SBR build is the Super Semi Automatic, or SSA trigger. The SSA fits my bill of both durable and smooth, it is a 2-stage trigger at 4.5 lbs. with 2.5 lbs. on the first stage and 2 lbs. on the second with a shorter reset and travel distance compared to a stock G.I. single stage. It's one hell of a trigger, it really is hard to go back to any other trigger after this one.

There are 'drop-in' trigger modules available on the market as well from companies such as Timney and Wilson Combat. The self contained drop-in units are very interesting triggers and without a doubt shoot well and worth a look. It certainly does make installation a snap.

Another trigger type is the adjustable trigger which is neat that the shooter can adjust the trigger to his or her's heart's content but I question the complicated trigger assembly's durability as well as trigger pull repeatability. With additional small parts and set screws come smaller parts to break and set screws to walk after each shot. Granted, the fire control group on an AR-15 isn't subjected directly to the full concussive force of the shot, but the gun still vibrates and the bolt still slaps the hammer down. I have spoken to other shooters who loved an adjustable trigger the first three months but over time became frustrated with the inconsistent trigger pull from the set screws walking or fouling getting displaced between the additional spaces on an adjustable trigger which ever so slightly re-adjusts the trigger. I will also concede that fouling will still affect non-adjustable triggers but to be fair, there are more nooks and crannies for crap to get in to on an adjustable trigger. Is this hearsay in regards to adjustable triggers? Certainly is as with my current opinion of what an adjustable trigger is, it does not fit my usability standards as more parts are introduced and the system more complex, more points of failure exist and to me that is not a durable trigger and I am not willing to spend money on one in order to have enough trigger time to find out either. If there is a company out there who wish to send me a trigger to evaluate, I am open to the idea and will test it thoroughly without a biased ending in mind.

There are still numerous triggers available and would be here a very long time if I were to write out each one, I am not here to pit one trigger against another nor claim what trigger is the best as the criteria for best are subjective to each individual and usage. What I hope to accomplish at the end of this article is for you to decided which kind of trigger pull you may find beneficial and to give enough knowledge to be able to see past the marketing hype.

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