Guest post by Glen Zediker, author of The Competitive AR15: Builders Guide.
Out of their boxes, AR-15 triggers just aren’t good. There are a few kind euphemisms written to describe them, but I’m not so nice. It’s a bad trigger. It’s heavy, sticky, lots of creep, often inconsistent shot to shot. It’s not the worst trigger—that’s probably an H&K.
But no one really can be too critical of a trigger that’s made for a service-use rifle. Given the need to pass the “drop tests” and also given that many users are not experienced and skilled marksmen, there’s a logic and necessity in play that precludes incorporating a light break weight and crispy action to the ignition switch of an AR-15.
I’m no engineer, but I know enough who have a good opinion, and the essential opinion is that we can just forget about modifying a stock trigger to perform better, as is possible with many other designs, most notably the M1A/M1. Now, that’s a trigger, or can be.
Anyhow, an issue AR-15 trigger could be modified to be much better from the shooter-side of the equation, but the parts that need to be modified are hardened. This hardening doesn’t run too deep into the metal, so, when the engagement areas and angles are changed, the improvement is short-lived. It will not endure.
Back in the day, which was not really that long ago, a few of us would install a shorter pistol-grip retaining screw and run a headless duplicate up into the upper receiver in front of it (grip screw went in behind). Done carefully, this screw can be turned in against the trigger body, pushing up on the trigger body and creating a “pre-pull” sort of effect. Done correctly (which mostly means not getting too greedy), it works fine; done incorrectly, it’s unsafe or non-functional, or both. I do not recommend this, so I’m being purposefully vague on the details.
Point is that the only real way to improve the trigger on your AR-15 is to replace it.
And here’s the first thing of consequence I have to say about that: Consider the use the firearm is put to. If your interest or needs involve tactical-style deployment or any manner of very-rapid-fire exercises, you might not want a true competition-quality trigger installed, or, if you do, you don’t want to get too greedy with refining its weight downward. This is mostly a reliability issue. If a trigger malfunctions on a competitive shooting range, it’s one thing; if it malfunctions on a two-way shooting range, it’s something entirely else.
For the “big-chassis” ARs, the AR-10/SR-25 type firearms, be forewarned that not all aftermarket AR-15 triggers will maintain function absolutely. The reason isn’t the recoil, it’s the rebound. When that huge bolt-carrier assembly slams home, it can trip the disconnector out of its engagement. The rifle is unlikely to inadvertently fire, but the trigger won’t be reset for another use.
Let’s look at a few simple and therefore often overlooked factors in trigger performance and function:
It can be argued that a rifle runs on springs, and especially a semiauto. When it’s possible, I install chrome silicon (CS) springs in all my triggers. Some of the drop-in triggers and other proprietary designs, like the Jewell, don’t use conventional-format springs. Most others do.
The advantages to better springs can be better performance, but mostly its durability. Chrome silicon springs just don’t change, even after hundreds of thousands of cycles. Music wire changes and changes quickly. It also continues to change. These changes may not be apparent to all shooters, but for those who get picky about their triggers, and also for those whose triggers must meet minimum weight requirements, it matters.
Chrome silicon springs also have different performance characteristics than music wire, most notably that the rebound force is relatively greater than the compression force. That means, for instance, that a CS spring will propel a hammer faster at a lighter spring “weight” compared to a music-wire spring.
A lighter-resistance trigger-return spring can reduce pull weight. A lighter-weight hammer spring can do the same. This spring holds the tension, and therefore resistance, between the hammer and sear. It’s not going to be a miracle if you install a spring package in a stock trigger, but better is better, and it will seem better.
On the other end of the spectrum, extra-power hammer springs are a double-edged enhancement. The only application, in my view, for this piece is to speed lock-time for a rifle equipped with an aftermarket trigger. Otherwise, the extra resistance makes stock trigger action even worse. If the hammer/sear engagement break is match-grade clean, it’s not noticeable. (Lock-time, in this reference, is the time elapsed between hammer release and hammer strike on the firing pin. Faster is better.)
Of course, that spring also needs to be reset on the rebound of the bolt carrier assembly. Mostly, it’s the extra pressure (continual pressure) from its higher coiling force that can increase wear on the engagement points and on the hammer pin. Speaking from experience, extra-power hammer springs are not worth it. When I tried this trick, my trigger kept changing, and it actually eventually ruined the trigger.
The only spring “trick” that works, and works well for me, is doubling up the trigger-return spring. Now, this is a very-narrow-scope enhancement. NRA High Power Rifle Service Rifle rules mandate a minimum of a 4.5-pound trigger pull. On a two-stage trigger, the first stage plus the second stage equals overall weight, so by increasing the first stage resistance (with the double spring), I can lighten the second-stage break weight. Again, it’s a pretty specialized need.
Elsewhere, trigger lubrication is important in an AR-15. I keep my competition triggers heavily lubed. I keep grease on the stressed areas, like the hammer/sear engagement, and oil on the pin areas. Something containing boron nitride is the best I’ve found.
Trigger pins make a difference when they are what they should be. Some aftermarket triggers include their own pin set, and it’s usually wise, and often necessary, to use those. However, when it’s possible I use pins from KNS Precision, Inc. It’s possible when KNS pins match the configuration of the pins they replace. These are dimensioned correctly, and they are straight, which really means concentric.
Since the installation points for an AR-15 trigger incorporate the lower receiver, the dimensional match between the pins and the receiver holes matters. Ideally, the pins won’t rotate within their enclosures — the pins stay still and the hammer and trigger rotate. There are pins with locking mechanisms, and those always go on my match rifles.
What you don’t want is wobble. If the pins have excessive free movement, which I say is any free movement, then the mechanisms can cam, or rotate on an eccentric, and, if that happens, the trigger pull can change.
As a result, there eventually will be some wear in the hammer-pin holes, but not usually the trigger-pin holes. That’s because the spring force imparted by the hammer is much higher, and the receiver is aluminum.
It’s fine-tuning to get a correct fit on conventional pins, and competition-oriented builders know how to tighten a loose pin fit. It involves careful peening. Oversized pins are available, including those shipped with pinhole reamers to match diameters perfectly.
Have you replaced your AR-15 trigger? Which one works best for you? Share it with others in the comment section.
Glen Zediker is the owner of Zediker Publishing, which has published detailed books on firearms for 25 years. Titles include The Competitive AR15: Builders Guide; The Competitive AR15: The Ultimate Technical Guide, The Competitive AR15: The Mouse That Roared, Handloading For Competition, The Rifleman’s Guide To Rimfire Ammunition, Service Rifle Slings, and Slings & Things. He has worked professionally with some of the greatest shooters on the planet, as well as leading industry “insider” rifle builders, manufacturers, and proven authorities on gunsmithing, barrel making, parts design and manufacture, and handloading. And he does pretty well on the line: Glen is a card-carrying NRA High Master, and he earned that classification in NRA High Power Rifle using an AR-15 Service Rifle.