Airborne Arms “Geronimo” AR-15 Trigger

I’ll tell you right away that the most interesting feature of this AR-15 trigger is the removable or interchangeable trigger shoe. That feature is a part of what Airborne Arms calls M.S.A.T. (Modular Shooter Adaptive Trigger) technology. The trigger shoe attaches to the base via a T-slot and is held in place by a set screw.

The trigger is called Geronimo in honor of the 509th Airborne infantry regiment. The Geronimo trigger comes with a red color straight trigger shoe. However, the company is designing and will shortly release other shapes and colors, too. The shoe also has machined out surfaces from either side to aid the consistency of trigger finger placement.

The trigger parts are made of hardened A2 tool steel with the exception of the trigger shoe which is made of 7075 T6 aluminum (anodized). It is a single stage trigger with hand polished interacting surfaces. Hammer shape is also different from stock AR-15 one. Geronimo trigger comes with two different weight hammer springs. The trigger pull weight is 3 – 3.5 lbs with the light (yellow) hammer spring and 4 – 4.5 lbs with the heavy (red) spring. That variation of pull weights also depends on where exactly on the shoe you place your trigger finger.

Some of Geronimo trigger parts are made by JP Enterprises. Particularly, the anti-walk pins, as well as two hammer springs and the trigger spring.

This trigger is available through the Airborne Arms website at MSRP of $189.95 and as the company says, it is “designed, cast, machined and ground in the USA”.

Hrachya H

Being a lifelong firearms enthusiast, Hrachya always enjoys studying design, technology and history of guns and ammunition. His knowledge of Russian allows him to translate and make Russian/Soviet/Combloc small arms related information available for the English speaking audience.
Should you need to contact him, feel free to shoot him a message at


  • Sunshine_Shooter

    Modular trigger shoes. An idea who’s (whose?) time has come?

    • Haulin’ Oats

      I think HiPerfire and Elftman beat them to it.

  • Phillip Cooper

    Cast? Why on earth would you cast these parts?

    • Christian Hedegaard-Schou

      Uh, pretty much every single milspec trigger on the planet is investment cast from steel then machined to spec.

      You use casting because it’s an inexpensive and reliable way to make complex high quality parts that would be prohibitively expensive to machine from billet.

      You can bet your Geisselle trigger is cast as well.

      • A.WChuck

        School is in session.

      • Matt

        Inexpensive? I would hate to see what these four pieces of metal would cost if not cast!

    • PK

      Try to find a modern military trigger that isn’t cast and then case hardened. You’re going to look for a while, as it’s cheaper, easier, and much faster to make the FCG a few million times by casting than by any other process.

  • Steven Calvaresi

    Meh….I’ll stick with my HIPERFIRE…..

  • Vhyrus

    Ya know, not every single part made for an AR has to have a cool abbreviation. You could have simply called it a modular trigger and we would buy it. Just sayin.

    • it’s just Boris

      Well, perhaps not at that price, however.

    • Haulin’ Oats

      It’s an acronym.

  • DanGoodShot

    A new AR trigger hits the market!! Oh boy! Really though, there’s got to be a new category put in the Guinness Book of World Records for the firearm with the largest amount of aftermarket triggers. Is there anybody on this Earth that doesn’t make a trigger for the AR/AR type now? (Just to be clear, cuz it doesn’t always translate well over the interweb, that was sarcasm. ;))


    OFF TOPIC – what is the lightest off the shelf complete AR?

    • Anonymoose

      There was one really goofy one that was like 4lbs. I think you’re best building such a gun yourself, and using a Sabertube, a BCM 14.5″ ELW barrel with a pinned titanium muzzle device, and Brigand Arms handguard. I wouldn’t use skeletonized receivers as that could compromise reliability.

    • Kyle

      Try looking at the JP Ultralight Ready Rifle. It’s meant for 3 gun nation shooting, but comes in a svelte 5.6 lbs for the 223 and 7.4 lbs for the .308 version.

  • USMC_grunt2009-2013

    Pass. I’ll wait for “The Old Breed” Trigger from Jarhead Arms.

  • Haulin’ Oats

    Geissele uses S7 billet tool steel for all of their triggers.

    • Kyle

      No they do not, their triggers are investment cast from S7 tool steel. The sear surfaces are likely wire EDM. Please do not state incorrect information as fact. It doesn’t help the quality of the website.

      • Haulin’ Oats

        From the SSA PDF.

        1. Performance Advantages for the Shooter
        • The Geissele SSA has a pull weight of about 4.5lb. 2.5 lbs on the first stage and 2lb on the second stage. The pull weights and sear engagement are non adjustable by the shooter.
        • Trigger and hammer are made from quality tool steel
        • Sear surfaces are cut by a wire edm machine. Sears cut this way are very accurate and the non-directional surface finish of the wire edm gives a smooth trigger pull without the associated grittiness of directional machining marks left by a milling cutter.

        • Kyle

          You realize you proved nothing, right? In fact, you’ve given me more proof than yourself. Thanks.

  • Kyle

    I’m pretty sure it works exactly as marketed. It even states on their website what ammo it should be used with. It’s only “questionable reliability” to the armchair commando brethren.

  • Christian Hedegaard-Schou

    They definitely do not make their triggers from wire EDM. You can see the casting marks on all their triggers and hammers on their product photos.

    They’re clearly investment cast like almost every other trigger in the industry.

    It’s possible they use wire edm for the sear surfaces though, that wouldn’t surprise me.

  • Christian Hedegaard-Schou

    Here’s a quote from Bill himself:

    “To follow up on tactical1’s post the three parts of my trigger (trigger/hammer/disconnector) are precision investment cast.

    [few things snipped]

    “Why did I choose investment casting? A couple of reasons. MIM can produce closer tolerance parts but the parts are weaker and highly subject to process variables. Tooling cost is very high and min lots were 10,000 parts. I wish I could sell that many! Available materials are also very limited.

    Forging can produce a good part but only the hammer and disconnector geometry can be forged, the trigger cannot. Forging also leaves a ‘trim flash’ and draft around the outside edges of the parts. Since the edges do work this flash would need to be removed (the front outside part of the magwell on a lot of AR lowers has this trim flash). A lot of additional machining would be needed.

    Cutting from barstock would add 50% to the cost of the trigger. It will not necessarily make a ‘better’ part than casting as I have seen my share of defects in wrought material. On the other hand there are more material choices in barstock than MIM (forgings are also made from barstock so there are also more options for forging). This being said I do very limited amounts of barstock select fire triggers for customers in the US SOCOM community….not because they are better per se but they have requirements such that the fixed geometry of my investment castings would need to be changed. In the next 3-4 months you will see the semi-auto version of this trigger commercially available.

    With investment castings tooling cost is reasonable, lots sizes are ok at 1000pcs and I can design in all the nice little rounds and features that would be big $$ to machine in. I also have unlimited design freedom for alloy choice. My foundry will make me a custom melt. They have bins of low carbon scrap, chromium, manganese, silicon, vanadium, tungsten, etc and they cook each melt individually. This has allowed me to use an semi-custom aerospace alloy from the 1960s that is no longer commercially available. With the advanced heat treating processes available today I felt it was the best choice to balance hardness, resistance to impact and wear. So far it has proven to be a good choice.

    The ‘sprues’ that can be seen on the outside of the parts are ejector pin marks from the wax pattern that is made in the mold during the investment process.

    As for castings being cheap, well….jet turbine blades are cast, medical implants are cast, missile components are cast……. We have all seen cheap castings that break so they get a bad rap. I have been in foundries that are downright scary and no way that you would want to put castings in your weapon from there. I have also been in steel mills that do predominately nuclear stainless plate (some of our wonderful barstock) that were worse. The foundry I use looks like an operating room, robotics all over the place along with dedicated foundry workers to give each part a human touch. The engineering staff are all shooters and they take a personal interest in my parts. If the castings they make were cheap and inferior I would not use them.

    Well, I hope the above dissertation did not bore anyone. I would be glad to answer any other questions.

    If you will be at Perry this year look me up at White Oak Precision…..I will be there with John Holliger helping shooters.

    The Best,