Throwback Thursday: AR-15 Two-Stage Triggers

By Glen Zediker published on in Gun Gear

In my estimation, a two-stage trigger in any rifle offers the most secure, precise, and safest function. Two-stage triggers appeared in U.S.-issue service rifles, such as the 1903, M1, M14. But for the AR-15/M16, it took the civilian-side aftermarket to create the two-stage trigger. The main reason other military-use rifles carried two-stage triggers is, primarily, because they are safer. There are other attributes to discuss, but safety is the main point in favor of a two-stage.

There are a good many two-stage triggers available now for the AR-style rifle platform. Development of available adaptations has been ongoing after introduction of the original and patented design by Charlie Milazzo. Most are knock-offs of his MKII; some are as good, some may be better, but the majority, in my opinion, are also-rans. A lot of fine work goes into producing a truly good trigger.

Being able to ride the trigger face, taking up the first stage, riding it back out when needed, makes for radically better performance in less stable firing positions. I use the first-stage take-up as a sort of “switch” to engage myself with the upcoming shot. If it’s not right or I’m running out of air, back off, regroup, and then go again. This off and on tactic requires a lot more finesse if you’re using a single-stage. And, since engagement doesn’t change with the two-stage, neither does the trigger feel. Sometimes a little off and on can nudge a single-stage into a lighter break. Photo by Glen Zediker © 2015.

In competitive shooting, being able to ride the trigger face, taking up the first stage, then riding it back out when needed, makes for better performance in less-stable firing positions. On High Power competition targets, the author uses the first-stage take-up as a switch to engage the upcoming shot. If it’s not right or he’s running out of air, he backs off, regroups, and then goes again. This technique requires a lot more finesse if you’re using a single-stage trigger, he believes. And because engagement doesn’t change with the two-stage, neither does the trigger feel. Photo by Glen Zediker © 2015.

I’m often in the company of a gamut of AR-15 users, and the leading initial reactions from someone who first fires one of my competition guns results from the trigger function. “Whoa, how do you have so much creep in the trigger?” Fair question, because that’s what a two-stage trigger feels like. But from a functional standpoint, it’s not creep.

The two-stage trigger design features a tensioned first-stage movement or “take-up” prior to engaging the sear lever. The take-up of the first stage begins to minimize the amount of sear engagement, until it “bumps” into the second stage. This bump stops rearward trigger motion, indicating that the sears are then at minimum engagement. Depending on how the trigger has been adjusted, it may take only a few more ounces of rearward trigger pressure to cleanly overcome the second-stage weight and fire the shot. Because the sears are not minimized until the first stage is taken up makes a two-stage a safer trigger. Two-stage trigger sears have a large amount of sear overlapping until the first stage has been completely activated, that is, pulled through.

First stage added to the second stage is the total pull weight. So, it’s possible to take a majority of this total weight out of the pull in an effectively unnoticeable manner. A two-stage trigger is a better platform for breaking an accurate shot because it is easier for the shooter to feel the remaining additional weight (the second stage) as opposed to overcoming the total pull weight for a single-stage trigger. On my competition rifles, which have the very best two-stage triggers installed (and a whole lot of tuning time expended), I set the second stage to a relatively light weight.

Again, the safety point: If we have a second-stage break weight of 1 pound, after overcoming, say, 3 pounds of first-stage takeup, that is a far safer trigger than the 1-pound break weight single-stage necessary to duplicate the effective break weight of the “4-pound” two-stage. Follow?

Unlike a single-stage (which simply releases after so much pressure is applied, with no prior movement), the shooter can put his finger on the two-stage trigger face, prepare for his shot, and then reconsider it. Back it out, and start it over. With a single stage, when the finger goes on the trigger, the next thing that happens is the shot, or the finger comes away from the trigger face entirely to stop the process. There’s much more “connection” controlling a two-stage let-off.

Here’s the original, the MKII by Charlie Milazzo. A long-time competition M1A builder, Charlie figured out how to do the two-stage for the AR-platform. Look closely at the illustrations and see how sear engagement changes from first stage to second stage. There’s a whopping lot of sear engagement prior to initiating the pull though the first stage, and a very “crisp” break from minimum engagement waiting after the bump when the first stage has ended. In a single-stage, such minimal engagement is necessary to get a crispy break, but it’s not as safe because it’s minimal from the get-go. In a true two-stage, releasing back through the first stage take-up also returns sear engagement to where it was. Another minor point, with major influence, is that since sear engagement returns to its formerly generous self after a shot, there’s not going to be any “tripping” of the sear as there can be with a single-stage that’s adjusted to a light weight. This can happen from the shock of bolt carrier assembly inertia. For this reason, it’s possible to attain a lower actual break weight with a two-stage. Photo by Glen Zediker © 2015.

Here’s the original MKII two-stage trigger by Charlie Milazzo, a long-time competition M1A builder. Look closely at the illustrations and see how the sear engagement changes from first stage to second stage. There’s a lot of sear engagement prior to initiating the pull through the first stage, and minimum engagement when the first stage has ended. In a single-stage trigger, such minimal engagement is necessary to get a crispy break, but it’s not as safe because it’s minimal from the get-go. In a true two-stage, working the first stage take-up also returns sear engagement to where it was. Another minor point is there’s not going to be any “tripping” of the sear as there can be with a single-stage that’s adjusted to a light weight. Photo by Glen Zediker © 2015.

Better is better. The question is always how good do you want? The “drop-in” and non-adjustable two-stage triggers out there are better than almost all stock triggers, immeasurably better, in my estimation. That said, tuning two-stage triggers requires a little creativity, but the better two-stage (and single-stage) “match” triggers have provisions for second-stage engagement adjustment. First-stage takeup weight can be adjusted with altering or replacing trigger return springs.

What’s less than ideal about two-stage triggers? Foremost is cost. But that’s something each shooter can decide to absorb, or not.

Second, I’m not convinced they are all reliable. I’ve not had one of mine malfunction, but I have had them change and require tune-up. The only trigger malfunctions I’ve encountered have been in tricked-up single-stage units. Keep a two-stage model well lubricated and clean, and it will deliver consistent let-off results, in my experience.

Another factor to note is that the distance to reset is greater with every two-stage I’ve encountered. By that I mean, how far the trigger must move forward after firing to reset the hammer for the next shot. If someone is trying to shoot rapid-fire as quickly as possible, a two-stage will slow things down. That was one of the first things I noticed when I first fired an AR-15 two-stage trigger. Compared to my previous competition NRA Service Rifle, the M1A, it felt like an eternity before I could get settled in for my next shot. The trigger in the M1A can be tuned so there is only a miniscule lessening of pressure on the trigger face necessary to reset, so it’s possible to shooter faster when the conditions and course warrant it.

Still, after you get accustomed to one in your AR-style rifle, a two-stage is the only way to go, in my opinion. A two-stage not only allows for more precision in firing, but it’s safer to use.

Do you own any two-stage triggers? What do you like, or not like, about them? Tell us in the comments below:

 

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, barrelmaking, 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. Correspond with him here.

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Comments (17)

    • rb59639

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      I have two large frame and eight small frame ar platform rifles. I built three using ALG QMS triggers and one with the ACT trigger, all using JP springs. One has a James Madison trigger, four have CMC’s. Of my two latest builds, one is a Grendel with a Elftmann 3-Gun and another 5.56 with Geissele’s new SSP single stage.

      I don’t know what it will take to get me to try a 2-stage trigger, I’m just not convinced of the need. To me, and I know it’s not right, a 2-stage just seems like a single stage trigger with a lot of creep. I’ve yet to have any safety issues with any of my single stage triggers, and I’m very comfortable knowing the amount of pressure I can apply before these triggers break.

      Reply

  • Charles Inglett

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    I have 2 AR’s. One has a Giselle 2 stage trigger with an optic. This rifle is set up as a coyote rifle. The other has a Giselle mil spec trigger on a carbine for home defense. The mil spec has a crisper break within mil speck. The 2 stage is an amazing trigger that allows a shooter to squeeze the shot between the heart beats. Reset is slower. Where one shot accuracy is essential the two stage is my go t rifle. Where speed is the order of the day Mil spec rules.

    Reply

  • Labman

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    I have owned a Bushmaster Varminter since the ban was lifted and it came with a 24″ fluted bbl., target crown, matched bolt and chamber and a 2-stage competition trigger. I had never shot a 2-stage before but once I got used to it, I was in love. The gun is their DCM competition rifle with a long 1:9 barrel and it really shoots. It favors a 60 gr. Hornady V-max pushed at 3100 and best group to date at 100yds is 6 shots into .29 inches. It shoots consistently under 1/2 in. off the bench and I attribute a lot of that accuracy to the quality 2-stage trigger. The gun carries that tight sub MOA out to 300 yds and is great for prairie dogs and other critters.

    I recently acquired a Bushmaster XM15 for play and found the military trigger not to my liking so I have been looking at triggers and this article has got me looking at 2-stage again. I’m not certain whether I’ll go 2-stage because I might want to set it up for 3-gun and have a need for speed. I’m still researching but I do know for squeezing every bit of accuracy out of a gun, 2-stage is definitely the way to go.

    Reply

    • JohnR

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      I also own a Bushmaster Varmiter I brought when they first came out. Love the 2 stage trigger and all the time I’ve had it I’ve only had to replace the gas rings and main trigger spring.
      Also own a Swiss K-31 made in 1943 that has a smooth as silk two stage trigger.

      Reply

  • victor

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    I have Stag Arms model 8, how do I determine the correct replacement trigger. Are there different in size for the trigger pins to secure in the lower receiver. That is question do I measure the pin or the hole they side into. Still learning about AR-15, What is the advantage of two stage trigger or is there a noticeable difference.

    Reply

    • mach37

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      You can post a question to CTD on the information page of the product you are interested in, like I did about the Timney 667S single stage trigger. I got an immediate reply, which was that “small pin” – 0.154″ pins – are standard in 21st century ARs, which my Eagle-15 is. I love my Timney and would buy it again, even after reading this article on two-stage triggers.

      Reply

  • Gary B

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    I have a Armalite AR=10 with their NM two stage trigger and I put a Ruger 452 two stage non-adjustable trigger IN a Daniels Defense DDM4 Version 3 (older one) as it had a mil-spec trigger. The Ruger trigger is great.
    I also have a fresh build that I used a Tac-Con 241 trigger that has three positions for it’s selector (Safe, Auto Reset, and two-stage) it works okay in the two stage mode, but not as nifty as the Ruger.

    Reply

  • Allen Wrigley

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    With the addition of a muzzle brake t my My Ruger SR556SC 16.12″, the rifle would no longer fit in my transport cases, so I examined probable changes in ballistics and functionality. Ballistics calculations showed that a 1.00” cut would result in negligible changes at the elevations published for the ACOG TF-31F scope I was using, designed for use with 62gr M855 “green-tip” ammunition at a MV of 3050 fps, as fired from the M16A4 (20 inch barrel). I was using the same ammunition at a MV of 2938 fps fired from the Ruger having the 16.12” barrel..

    According to published information, with 1.75″ cut off the barrel to a rifled length of 14.37″, the MV would decrease from 2938 to 2850 fps, and the exit pressure would increase from 6581 to 7288 psi. The literature stated that stability and functionality problems should be expected below a barrel length of 14.5″, so I looked at the 1′ cut in length.

    With 1.00″ cut off the barrel to a rifled length of 15.12″: I figured the MV should decrease from 2938 to 2888 fps, and exit (uncork) pressure should increase from 6581 to 7056 psi, so I chose the 1″ barrel cut and recrown, resulting in an overall length increase with the QM muzzle brake (permanently) installed of (- 1.0″ + 2.4″ -0.625″), or 0.775″, and no significant change in functionality or ballistics.

    I had already equipped the rifle with a Geiselle two-stage DMR trigger set at 4.5 lab, the first stage set at 3.75 lbs, and the second stage set to break like an icicle at an additional 0.75 lbs. The rifle was fired off of bags, front and rear. The trial yielded a seven-shot 1.0 MOA group with six in the X-ring of a 100 yard target at 100 yards. Three other rounds were not far out of the 1 MOA group.

    Apparently, I inadvertently changed the barrel dynamics by shortening the barrel and adding weight to the end, because I was never previously able to shoot less than 1.25 MOA, using bags both front and rear.

    Without the two-stage trigger, the sub-MOA group would not have been possible.

    Reply

  • Chris Francis

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    I have used Del-ton two stage lower parts kit in two of my recent builds. This is a very smooth trigger pull. It is not a high end adjustable setup, but it costs 3 or 4 times less than one of those. Hammer shape is like the MkII shown above. I recommend buying the whole parts kit as it’s only about 25% more than the trigger group by itself. Even if you just replace the trigger group, doesn’t hurt to have some spares for those springs and detents that can go flying when assembling a lower.

    Reply

  • Tim

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    I have a 2 stage trigger on a CZ 270. I love it. It feels like creep on the 1st stage and often people mention it when they shoot it. I love it because you can use it in 2 ways. You can ease to the 2nd stage, make any minor adjustments or breath, then pull the second. You can also pull in a smooth motion all the way through and the second stage breaks before you have a chance to flinch, but you don’t disrupt your shot by putting the trigger into motion the way a single stage with no creep does. I think it takes away the need for a high disciplined trigger pull that, lets face it, sucks when you have only one shot to bag a deer or a pig and the adrenaline is pumping bigtime.

    Reply

  • Roy Holbert

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    2 stage triggers are wonderful things and truly great for the sometimes inexperienced shooters that you get in the military. As an experienced shooter and hunter, upon entering the military, I had a terrible time becoming accustom to them. That discussion aside; outside of the military, I discovered ‘set’ triggers, both single and double and instantly fell in love with them. Perhaps it would be too much to hope for, to see them on military rifles. Not the main combat rifles, but, instead in special purpose rifles, say for snipers and such,

    Reply

  • Mike in Flag

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    I love my two stage triggers in all my ARs, but I understand that to be competitive in 3GUN a single stage trigger is the way to go. That’s for my next build.

    Reply

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