Gear, Parts and Accessories

AR-15 Trigger Basics

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:

Springs

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.

Lubrication

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.

Pins

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.

The Mission of Cheaper Than Dirt!'s blog, The Shooter's Log, is to provide information—not opinions—to our customers and the shooting community. We want you, our readers, to be able to make informed decisions. The information provided here does not represent the views of Cheaper Than Dirt!

Comments (28)

  1. Before I even bought my first AR (Ruger AR 556) I had a CMC straight competition trigger for it. It’s crisp and light, And aids in accurate fire. It can be “short-stroked” however.

  2. I installed the Elftmann match trigger on my Armalite AR10, and it is absolutely amazing. Easily adjustable from 2.75 to 4 lbs while mounted in the gun, Trigger and hammer run on needle bearings. Stock trigger and hammer pins are locked tightly in place with set screws. Less than 1/4 inch trigger pull and reset, glass smooth break, audible and tactile reset. 100% drop safe to boot. Lifetime guarantee.

  3. @Vector16

    The article is about how to improve OEM AR triggers which I think we can all agree are sticky, gritty and heavy at best and inconsistent and a general fail at worst. That being the topic, I agree that aftermarket triggers are the only solution. If you are content with these inherent trigger issues then by all means go for it, but when you can get a Rock River Arms Single Stage Trigger Kit for $35 or a Two Stage NATIONAL MATCH Trigger kit for $62 (see their website), I can’t understand why you would skimp on accuracy, you say you spent the extra $$ on a Nikon scope, why not splurge on a trigger kit too?

    My point is that you don’t have to break the bank to improve on the OEM trigger; Midway USA has the KNS non rotating pin set for $27. I just don’t see why you have to sacrifice when the cost is so low.

    I have built 6 AR’s; two of my own, two for my son and two for friends and I put RRA triggers and KNS pin sets in each of them and have had no problems. I’d love to spend $240 on a Geissele SSA-E trigger, but unless you are shooting competitively there is no necessity. My AR’s are just right for 1 1/2″ groups at 200M and for CQB if necessary. They are not spiffed up Daniel Defense, but they do the job for me.

    Just my 2mm…

  4. for the $65.00 the ALG- ACT triggers are outstanding. I upped the anti and bought the Wilson Combat TTU trigger and considering the $200 difference in price, I could not tell the difference in performance.
    My new go to triggers are the HiperFire straight triggers 24C but all are great. I have one in my FaxonArms 7.62×39 with the red hammer spring that ignited very consistently the Russian ammo and I have one in my LaRue Sniper. In all areas of performance they exceed expectations.

  5. Jewell triggers are used exclusively in all my Remington 700 varmint and competition rifles. Geissele 2-stage NM or Rock River Arms 2-stage NM triggers are in the AR’s. I tend to favor the Geissele triggers for the AR’s for their adjustability. Testing each trigger by repeatedly bumping the rifle’s butt on the concrete basement floor with a snap cap in the chamber, and as light as the triggers are, not one has ever tripped. One has to use great caution when adjusting any trigger.

  6. as a retired gunsmith i have to say upfront im not a big fan of a r rifles or plastic hand guns. most people i meet have the low end versions of the a r and no trigger in the world will make them shoot consistent sub minute of angle groups. (please dont reply with the my used$400 bushmaster shoots 1/4 ” groups,ive heard the stories but havent seen it done) if you own one of the high dollar models it should already have a good trigger upgrade. for most shooters your best bet is to buy a nice wood stocked bolt gun in the $700-$1000 range and shoot repeatable 1/2″ groups. got $2000 to spend get a cooper or montanna rifle co bolt gun and see how neat it is to shoot 1 hole groups out of the box. if the gun wont shoot like this for you,you need to forget everything you learned in the military or the law enforcement acadamy and find a bench rest shooter with the time to teach you how to shoot.yes i know those guys are nuts but they do know how to shoot. lastly dont scrimp on your optics you wont be soory. enjoy hitting a beer can at 250 yards.an accurate rifle in the hands of a good shooter is a joy to behold!

    1. Apparently you retired too early to see today’s AR 15 type carbines and rifles.
      Even the least expensive tend to shoot very accurately, especially the direct impingement type.
      An inexpensive AR with good ammo is a thing of beauty. A $35 Rock River Single stage upgrade makes it even better.
      You certainly don’t have to spend $2000 to plink cans.
      Those low end ARs can hit a can any day.

  7. I was very unhappy with the mill spec trigger in my S&W AR15-sport.
    My first new trigger is a del ton two stage, it made a big difference in accuracy. My second trigger is from Anderson Arms. It is there ss trigger, hammer package. I like the Anderson from the stand point that the mass has been lowered on the hammer. Happy with both triggers

  8. The $0.50 set screw and light polishing can take a stock, 4.5-5lb gritty trigger to a 3.5lb, smooth, single stage trigger …perfectly fine for the average AR. If one plans to shoot 8k rounds or run without lube, YES, you will need to replace the trigger and hammer because the hardening is thin in the areas as the article mentions and polishing tends to shorten the life.
    Running 7.62x39mm ammo through an AR is absolute fun! But it has 3 problems; accuracy, broken extractors, and light primer strikes.
    Cheap Russian made ammo has a seriously hard primer, one that stock AR hammer springs will not reliably ignite. Enter the ~$200 HiperFire 243G. It has a unique design using supplemental over-center, hammer springs. It comes with three sets of hammer springs. The stiffest (silver) springs provide the hardest primer strike (and shortest lock time) but also provides the lightest trigger pull (at ~2lb). The middle (yellow) springs provide a 2.5lb pull. And the lightest (blue) springs, with 3lb pull, completely eliminated light primer strikes. The trigger breaks crisp and clean with no creep, minimal over travel, and a positive reset. (BTW: 2lb is too light for a field gun.)
    Accuracy was improved using a 1:8 twist barrel (from 3.5″ with a 1:10 to 2.5″ – that’s average group size of 4 consecutive 5rd groups at 100yds off sandbags).
    Now about that extractor…. 😎

  9. Had a Bushmaster trigger that was creepy and gritty. Swapped the hammer for one out of a S&W Sport and accidentally created a really great two stage with a heavy initial pull, a sliding plateau and a crisp let off akin to a slicked up Garand. Neat but weird!

  10. With over 20yrs in the military and some of it with AMU I have quite a bit of experience with the M14 and M16 platforms. I found the timney triggers work well when installed correctly. Those extra set screws in the package are not extra. They are to be screwed down on top of the other set screws to keep anything from coming loose. When installed correctly I’ve yet to see one fail.

  11. I run Geissele SSA-E triggers in all of my ARs aside from one build from scratch job I did for the purpose of running a bumpfire stock. For that one I run an ALG Defense* ACT trigger with JP Enterprise’s yellow spring kit. That upgrade cost less than $75 total and it turned out to be awesome. Don’t get me wrong, it’s not the crisp precision of a true Geissele trigger, but for the money it is an outstanding upgrade.

    That being said, the Geissele SSA and SSA-E are the cream of the crop in replacement AR triggers, in my opinion. I won’t buy or build an AR without factoring the cost of one into my budget. That’s the harm in running one of these… once you go Geissele you’ll never be able to go back to a stock trigger.

    *If I recall correctly, ALG Defense is owned by Bill Geissele’s daughter.

    1. ALG is his wife Amy’s company. But thank you for your kind words about Geissele and ALG! I am an employee there and we all take pride in our work! Thank you!

  12. Okay, question time. But first some background. Working consecutive combo careers both in the military and as a Federal LEA, I have generally only ever experienced the stock equipment triggers as issued by each armory, and we are not allowed to modify personal weaponry we purchase for the job. I did get away with a Glock modified trigger once though.

    Now that I am rolling up on retirement I have had more opportunity (vacation time) to increase my personal weapons inventory and begun to play around more with upgrades. The only experience I have with high-end aftermarket triggers is a Timney adjustable trigger I installed in my second Mosin-Nagant which I sporterized recently for fun. With that, I’ve realized just how expensive a trigger upgrade can be. The trigger cost almost as much as I paid for the rifle, but I have yet to get out and test fire it to see if it was worth the price to upgrade yet.

    So my question is, as I expand further into the world of weapons tinkering and upgrades and learn of the great expense associated with better triggers, how does one determine which triggers are best for which rifles/handguns without spending a lot of money first to test them?

    Is there an all-around sure-bet trusted brand to stick with for all upgrades for all guns – say as in the Timney brand I bought, or do different manufacturers each make certain triggers for certain respective guns better than one another? If so, is there some type of a definitive guide or reference to help narrow down which brand triggers are best in which type guns? Or is it always going to be opinion based like everything else in the gun world? Thanks in advance…

    1. First a little background; after a 20 year career in the Army, followed by 10 years of gov contracting and LE/Military firearms instructing, I am not a ‘gun geek’ or early adopter of gadgets or black gun fashion crap. I only care about safety, reliability, and accuracy. I have been very fortunate to have had the oprotunity to burn through many hundreds of thousands of round other people paid for and I don’t even come close to knowing it all. If you can, find people with after-market triggers and shoot their guns. Another way to at least dry-fire test triggers is at trade shows or other expositions. Make them sell it to you! Otherwise, you can’t go wrong with most of the triggers mentioned here. I’m not a big fan of adjustable triggers, only because I have found no real advantage compaired to quality non-adjustable triggers. 4-5 pounds with a clean break, little overrunn, and positive reset that is reliable and safe under field conditions is all a Brother can ask for.

    2. @ Rocky,

      Excellent advice to look for and test aftermarket triggers at trade shows or other expositions. Since I usually purchase online (cheaper that way), I was contemplating how I could do just that, given my local gun stores don’t usually have aftermarket triggers readily available to test I was somewhat at a loss and hadn’t considered the trade shows. Thanks for the feedback.

    3. A guy with your resume can get into just about any event out there. I kind of pussed out on a strait recommendation, but if I were to give one it would be the POF. It is an excellent trigger and resonably priced. They offer a standard vertion and couple of variants on the theme. I personally like the standard trigger, but I’m a serious hard sell on new ideas. Most manufacturers offer a LE/Military discount, so use it!

    4. @ Rocky,

      I’m taking notes. Your input has already led to my research on reviews and comparisons between your recommendation of the POF line and the Geissele SSA-E triggers mentioned by Joe D. above. Thanks again.

    5. It’s hard to beat Geissele SSA or SSA-E, both two stage with either 4.5 or 3.5 lb total triiger pull. The SSA is the civilian version of the SSF SOPMOD trigger built for SOCOM. It would be difficult to get a better, more reliable trigger than an SSA.

      The Geissele Super Semi-Automatic (SSA®) trigger is a semi-automatic only version of Geissele Automatics’s Super Select-Fire trigger. The SSA is a 4.5lb. non-adjustable combat trigger that is a precision two-stage trigger and allows precise and accurate trigger control. The SSA’s two-stage design allows the trigger to be light enough for accurate and precise shots, but forgiving enough for CQB. The SSA is safety certified by Crane Naval Surface Warfare Center. It is recommended for demanding applications such as Law Enforcement use, Close Quarters Battle (CQB) and mid-range carbine work.

  13. I have 20 years on USGI triggers in the M16A1, A2 and M4 flavors … yes, for precision work, compared to my friend’s Savage bolt gun, military triggers suck! In the 2 AR builds I have done (1 large format, the other small) I have used JP adjustable triggers and anti-walk pins. Same size components for either format. The second was an updated and easier installation job than the first. Both involve red Loctite, and the excellent instructions provided (booklet and dvd) make it a job no worse than an oil change on your car. The adjusting screws control amount of overtravel after hammer release from sear, and in the first job, amount of sear engagement. After 10 or so dry fires to get the disconnector timed properly, it was time to start over and use the Loctite. Let the project sit 24 hours before any further stress on the lower – good time to work on the upper! So far no issues. The large AR was originally intended to be my deer rifle but my traitorous emperor decided he disliked black rifles (except the ones carried by his state Gestapo bodyguards, of course), so a vintage Remington semiauto 30-06 fills that role now. The ARs will see service when SHTF, the large in my hands, the small in my wife’s hands. Now if I could find body armor in sizes corresponding to her bras LOL?!?!

  14. I replaced the trigger on my XM15 with a drop in Timney single stage trigger and the trigger on my Bushmaster 450 with a two stage Geissele.

    My reasoning was that on a hunting rifle, the BM450, I would be taking deliberate shots that benefited from taking up the first stage to the point of shooting with a very light (3 lb) second stage. For tactical use and personal defense, a positive single stage would be better for a more rapid rate of fire with potentially little opportunity to set up the shot.

  15. A good trigger is a beautiful thing! It’s like a good fishing reel; I was perfectly happy with a $30 Walmart reel until I used my buddy’s $300 state of the art reel. I was ruined for ever!

    I good trigger is probably the best money we can spend on improving an AR for anything other than pure tactical use. AR’s from most reputable manufactures have good barrels and action components and they respond well to a simple trigger swap.

    I prefer a single-stage, but that’s just me. I find two-stage triggers actually slow me down during combat marksmanship type drills. Two-stage triggers are awesome for making tiny shot-groups at long range, if that’s your deal. I have extensively tested and used Geissele, POF, and Timney products. I have to give a nod to the POF due to it’s simple drop-in installation and the fact that I have never had an issue with them. I have had at least two Timney drop-ins fail me in a dangerous way (like fire twice; one on trigger squeeze and one on trigger re-set). Not good. The Geissele is outstanding too, and it looks like a GI trigger. It is what I run in my otherwise completely stock “work gun.”

  16. Okay. That’s all well and good. If you have the extra cash laying around you can go out and do all this stuff or go buy a tommy trigger for $300. Great. OR you can do the 25 cent thing that we all do to our guns anyway and polish the hell out of everything. OR do nothing.

    Be patient. Aim, breath, exhale, hold, fire. I am at a 3″ group @ 200 with my AR/M4. I do not mess with it a whole lot. I use Super Lube bearing grease on all contact points and Hoppies for bore lube. That’s it. Its a Del-Ton Echo 316. All stock but the hand guard and the Nikon scope. This kind of article is great for the people that can afford the Wilson Combats and the Daniel Defense `guns @ $3K to $18K. But not for the guy that buys froum CHEAPER THAN DIRT or Wally World.

    1. @Vector16,

      I have to say I agree with you on this for a couple of reasons. For all you serious gunaholics who love to tinker, more power to you. I am impressed by the knowledge of the people on this type of discussion thread, and it’s fun to read about and see some of these beautiful weapons.

      But first, exactly what you said. We’re talking about quite a lot of outlay here that could be spent on other things like ammo and supplies. Probably the most expensive guns I own are my M1A and Desert Eagles. Beyond that, I just don’t have the cash to spare.

      Second, IMHO, the more refined and finely tuned a firearm is, the more likely it is to fail under hard usage. As the article says, military weapons have to pass the drop test. This is exactly why Glocks and AKs are considered among the most reliable weapons in the world . . . they have plenty of wiggle room built into the tolerances. Military M4s are the same. I was once improving a fighting position with my Battle Buddy, and a load of dirt was inadvertently dropped on my weapon, right into the open dust cover and over the bolt assembly. My first thought was . . “Oh, sh^%.” I got the assembly out for a quick field cleaning, and it worked just fine. I do private security work now, and own two M4s and an AR (as well as a WASR that keeps on ticking) and they are working guns. They take a lot of abuse and always work.

      I know that these highly refined guns are fantastic on the range, and shoot groups off the bench or prone that my mostly stock guns couldn’t shoot, but I never failed to qualify Expert with Milspec rifles and pistols, and the whole idea behind military qualification is to kill the other guy before he kills you.

    2. I completely agree with Vector 16 and Mikial. As a service connected disabled Vietnam vet, my pension does not give me the luxury of buying the latest and greatest. My Bushmaster M4 was purchased because it was as close to my M16 as I could get. Minus Full Auto.
      I get creative by buying the best I can on a budget.
      These are a great read for the “average” G.I. Joe. Unfortunately they are out of my budgetary limits. Mikial is right, “kill the other guy before he kills you.

  17. I like the Geissele 2 stage Dynamic triggers. I especially like the Super Dynamic 3 Gun. The break is clean and the second stage makes sense holding after the break. The straight trigger itself leaves some getting used to but once you do, it is perfect. There is no looseness at all as long as the pins are not moving. The other Geisseles are as good and more conventional but with the same fineness. My first trigger upgrade was a standard Armalite 2 stage which was a good improvement but would not seem so for those who are not perfectionists. But, I like the 2 stage, even over the enhanced single stage. Almost any after market name brand trigger is an improvement over the OEMs. When I started out, I went to the CMMG single stage which was was not a noticeable improvement. After the Armalite, I tried an RRA 2 stage which was about the same as the Armalite but both were worth doing at the price. I am happy with Geissele. I have not tried the drop in trigger groups such as CMC or Timney etc. I just don’t like the idea of a modular trigger group because I am more comfortable with putting together the individual parts so I know more what is going on.

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