Product Design


The module box that contains the CMC trigger group is designed to keep side-to-side wall thickness as close to standard as possible. So, if a buildup of grease, grime, sand, or powder residue occurs, the internal parts still have the clearance to continue to function as the factory-standard designs would function under these conditions. Had the internal geometry been closed-in around the moving components, it wouldn't take much to contaminate the parts and lose clearances, resulting in malfunctions. The stainless-steel sheet metal module is a high-tech, close-tolerance, critical component with +/- .001" tolerances in areas critical to function. A high-quality component that is not easy or inexpensive to make.


No matter what methods are used to secure them, screws can and will come loose, and we have done everything possible to avoid Murphy's Law.

We all know that when Murphy's Law strike, it generally occurs at the worst possible times. Using screws to attach the trigger module to the receiver would offer no benefit and be counterproductive to the design objectives. Nor would screws secured with adhesives add to the effectiveness of the mechanism. The CMC design purposely does not rely on any screws or adhesives that could allow parts to loosen and cause a failure.


If a well-meaning, unqualified person can tamper with a perfectly functioning mechanism, they will. CMC can't allow that. Those who put a premium on reliability and the vast majority who understand the disadvantages wouldn't tolerate it.

Adjustability means additional parts would have to move in conjunction with the components that require movement. Adjustable features offer no real benefit to accuracy and could compromise reliability. Furthermore, due to the nature of CMC's Drop-in design, adjustability is not necessary.

Why is adjustability not necessary? The only valid reason that adjustability would serve any purpose in the AR rifle would be to reduce the install time of a non-drop-in trigger group that required many loose parts. Many AR rifle brand receivers are built to varying nominal dimensions and tolerances, even when based on military specifications. Many AR rifles are reverse engineered without reference to the military specs adding to the problem. To make a precision set of parts with the same geometry for each that functions reliably in every brand of AR is unlikely, and why we don't see complete sets of individual parts that can drop in without any fitting required.

The adjustability of a trigger group might seem convenient. However, it's best to have quickly interchangeable set weight fully enclosed triggers assembled by qualified, experienced technicians who have assembled and hand-tested each for safe and proper function. 


With a CMC AR Drop-In Trigger, you are buying consistency that narrows the remaining questions down to what gunsmith is qualified to insert two pins and proficiently determine the results have yielded safe and proper function.

If you take any CMC AR Trigger from one rifle, install it in another, and then another, and so on, the same level of AR gunsmithing skill applies. The lower receiver must be grossly outside the mil-spec geometry for the CMC Drop-In AR Trigger Group to not fit or not yield safe and proper function.


We believe the necessary elements to match precise trigger control with a fire control system that will dependably function up to the highest standards are experience, knowledge, state-of-the-art design, testing, tight tolerances, precision manufacturing, and quality control.

After years of producing and improving processes and geometry, the CMC Drop-In AR Trigger Group has brought every element of what yields Tactical Grade Quality up to the most demanding levels.


A clean, crisp trigger release and predetermined pull weight are crucial elements to any trigger group that allows the shooter's performance to meet the firearm's potential.

CMC's Drop-in AR Triggers are factory set to varying choices of trigger pull weights. A truly clean, crisp breaking trigger pull set at 3.5 lbs. seems much lighter to most casual shooters. However, suppose you are familiar with the outstanding marksmanship of competition shooters using a minimum 4.5 lb. trigger. In that case, you will not doubt what is possible with 3.5 lb. or even 2.5 lb. trigger pulls available with the CMC Trigger Groups.



These elements are critical to the overall performance of a world-class shooter but are also crucial to anyone who wants to demonstrate precision shooting.

Unlike traditional AR trigger groups, one of the most spectacular elements of the CMC AR Drop-in Trigger is that Tactical Grade Quality over-travel and take-up can be accomplished with geometry, without screws and other unnecessary moving parts. With the almost 20 years CMC's Triggers has been in production, the hundreds-of-thousands sold, and grateful customer feedback, CMC is confident that the design of their triggers' take-up and over-travel is right in the sweet spot. Plus, for the life of that trigger, it won't change because it's done with geometry and not moving parts that come loose.


How important is reliability to you? 

CMC's Drop-in AR Trigger gets outstanding combat reliability, service life, Tactical Grade Quality, and trigger pull without compromises like reduced power springs or sear/hammer engagement.

The cheap, easy ways to reduce trigger pull weights use minimal sear/hammer engagement and reduce spring rates on the trigger return and hammer springs. But CMC's way of thinking is that cheap, easy methods are counterproductive to the objectives of this design. 

  1. Reduced spring forces increase lock time (the time from when the trigger releases the hammer until the hammer strikes the firing pin), reducing accuracy potential. 
  2. Reduced spring forces can cause trigger groups to fail much easier in grimy, dusty, or fouled conditions. 
  3. Reduced spring force on the hammer causes light strikes of the firing pin on the cartridge primer. The potential for light strikes has two problems that are especially concerning. The rifles fail to discharge the round, or if the rifle is fired a lot without cleaning (especially in extreme environments), fouling can cause light strikes to occur long before they would have with full power springs. 

Springs – The springs used in CMC's Drop-in AR Trigger modules are custom made using the finest music wire spring materials available and are spec'd to replicate the forces of the springs used in military weapons. Resulting in reliable discharge with inexpensive military surplus ammo, faster hammerlock time to maximize accuracy, and longer-lasting reliability in various environments.

Engagement – The sear tip's engagement to the hammer cock notch is critical for reliable function under varying conditions. Other triggers reduce pull-weight by reducing engagement to the bare minimum. Maybe that's OK for bench rest rifles, match-only rifles or rifles always kept clean and carefully handled, and reliability is not of grave concern. However, the CMC Drop-in AR Trigger is well-suited to all the above uses without compromising reliability.

Surface Finishing – The surface finish is critical for obtaining that magic "feel" necessary with a Tactical Grade Quality trigger group. Every component of the CMC Drop-in Trigger maintains tolerances of +/- .001" (one-thousandth of an inch) or less wherever two critical surfaces engage or interface. Those exact tolerances apply to each hole location.

Materials – Using only the highest-grade materials, heat-treating specifications, and CMC's unique proprietary processes result from intensive studies by CMC's highly qualified engineers. 

Extreme Testing – To validate the engineering and design of CMC Trigger Groups, we implemented an extreme testing protocol. CMC commissioned an engineering firm to build a machine that replicates the cycle of an AR action. The carefully documented tests include 25,000+ round cycle testing of multiple groups, analyzing each component and its critical dimensions several times throughout the test. Then the same parts used in the 25,000+ round testing were live-fire tested for 500 more cycles and checked again, resulting in zero cracks, fractures, or failures of any kind. Therefore, every characteristic of the CMC Trigger Group undergoes hundreds of thousands of rounds of cycle testing to ensure reliability before releasing a design update.


Which AR rifles are compatible?

CMC Triggers offer all their Drop-in AR Trigger versions in SMALL PIN, LARGE PIN, and M&P 15-22 COMPOSITE PIN. 

The CMC Drop-in AR Trigger Groups are designed to fit any lower receiver manufactured to be within the standard military specifications for nominal dimensions and tolerances, except Colts® with sear blocks because the sear block is in the way of the trigger going into the lower.

If your AR rifle is NOT a Colt® or a Colt® produced before 1991 or after 2009, it will take a SMALL PIN (.154 Ø).

Colt is the only AR brand to produce both small and large diameter pins in their triggers. Colt AR-15 rifles produced between 1991 and late 2009 commonly take a LARGE PIN (.172 Ø).

The Smith & Wesson® M&P® 15-22 or any receiver wider than standard will use a SMALL PIN diameter but requires a longer pin length and will take an M&P 15-22 COMPOSITE PIN (.154 Ø).

If you are still unsure of the pin diameter needed for your rifle, you can measure by pressing a pin far enough out of the receiver to measure its diameter, .172 Ø for LARGE and 154 Ø for SMALL.

It's always recommended to have an experienced and qualified AR gunsmith to be the one to qualify safe and proper function of the trigger module.


CMC will refund the purchase price of any unaltered Drop-in AR Trigger Group within 30 days of purchase. Offer applies to purchases direct from CMC or participating dealers only.


With proper care, your CMC Trigger should last a lifetime. If your trigger should ever need adjustment, please return it for repair or replacement. CMC will refund the purchase price of any unaltered trigger or product within 30 days of purchase. Offer applies to purchases direct from CMC or participating dealers only.

Products returned from dealers to CMC for credit must include proof of the customer's purchase. Refund offer does not include the cost of shipping, handling, or other ancillary charges. Participating dealers are responsible for refunding their customers, and CMC will be responsible for refunding the CMC dealer upon receipt of the returned products.

Alteration, tampering, or disassembly of the CMC product voids all warranties, implied or expressed.