CMC AR-15/10 Curved Single Stage Drop-In Trigger Review

I have built several AR style rifles over the past years, yet all have been built off various lower receiver "build kits" and none of them have what I would consider as a "better than standard" trigger pull.  Most of them range from around 5.5 to 6.5 lbs of pulling force.  A couple of years ago I decided to setup a rifle specifically for hunting in wooded areas with most shots to be less than 100 yards (realistically less than 50 yards) and decided on  the 300 Blackout caliber for this purpose.  This rifle is shown below and I have been very pleased with this build, yet have always known a better trigger was in it's future.  As I was looking through the various Black Friday deals at Palmetto State Armory, I came across several drop-in triggers and in the end selected this CMC trigger that was advertised as having a 3.5 lbs trigger pull and purchased it at a bargain price of $99.99, which must have been a great price because they are now listing a price of $173.99.  The CMC website carries this 91501 model and they show a MSRP of $189.99.

Figure 1 - Rifle Build


During my reviews I like to compare my results to the manufacturers claims where possible so the following text in colored italics was taken directly from the CMC website on 12/12/23 and gives an Overview, Key Features, and Specifications for the CMC AR-15/10 Curved Single Stage Drop-In Trigger.  The , and are my way to keep up with details that I have covered in this review with either photos, commentary or both.  I may also add commentary after these marks as necessary to explain some items if needed.

CMC Triggers Single Stage AR15/10 are available in configurations for Small Pin, Large Pin and M&P 15/22 Trigger in multiple pull weights and Signature Flat, Curved or Combat Curved Bow. Manufactured in the Great State of Texas.

CMC’s innovative, self-contained and easy-to-install AR-15 trigger groups, have been completely re-tooled to maximize production capacities, incorporate new design enhancements and reduce cost. CMC’s AR-15 trigger groups have always yielded exceptional trigger pull dynamics for our tens of thousands of satisfied customers.


  • Single Stage Trigger Available Pull Weights: 2.5lb, 3.5lb, 4.5lb, 5.5lb and 6.6lb Purchased 3.5 lb version
  • Available Pin Sets: Small, Large and M&P 15/22 Purchased small pin version which is standard on most lowers today
  • Ultra-crisp trigger with no feel of creep prior to hammer release In general yes, but if you really work at trying to feel the creep there is a very slight amount
  • The trigger has a glass-smooth break with no feel of grittiness I agree
  • Minimal lock time is designed into the assembly using controlled hammer weight and balance activated by a rocket wire hammer spring, assuring repeatable function with either commercial or military grade ammunition
  • Trigger pull is factory pre-set and not user adjustable Yes no adjustment and mine averaged ~3.75 lbs
  • Positive trigger reset allows a quick follow up shot on target
  • Hand assembled, and hand tested I can believe this
  • Totally self-contained one-piece assembly
  • Comes with CMC Anti-Walk Pin Set Fits Yes you can call them anti-walk pins, but in reality standard pins will not work so these are the required pins for this configuration which happen to give the benefit of anti-walk pins
  • MIL-SPEC AR-15 and AR-10 style rifles Fit in my Spikes Tactical Lower
  • Made from 8620 Alloy Steel and S7 Tool Steel with machined tolerances of +/- .001″ Gonna take their word on it

The trigger assembly came packaged as shown below, which is nothing fancy, but good enough.  You can click on these photos or any others in this review to see a larger version allowing you to read or see better details.

Figure 2 - Front of Package                                     Figure 3 - Back of Package

This next series of photos shows the trigger assembly from the various primary sides.

Figure 4 - Top View

Figure 5 - Left View

Figure 6 - Bottom View

Figure 7 - Right View

The photo below shows that they liberally greased the sear contact area.  Not that it matters, but I was surprised to see the "nose" area of the sear appeared to have a rough looking surface with what appears to be machine marks.  Regardless, the trigger still measures an average of 3.75 pound trigger pull which was close enough for me to the advertised 3.5 pounds.

Figure 8 - Front View with Hammer Cocked

In this next photo I was trying to show that the sear face notch had a polished smooth surface to the point at which it looked like a mirror finish.

Figure 9 - Looking at Sear Notch

The trigger also came with the below items; two pins, four screws and two Torx keys.  CMC advertised these pins as anti-walk pins, which they are, but realistically they had to supply pins that had some other retaining device other than the standard detent in the middle of the pin because the trigger components don't contain the detent bar inside the middle of their pin holes.

Figure 10 - Trigger Pins and Torx Wrenches Supplied

I  made a YouTube video review showing the installation of the trigger plus other general review content that can be found by clicking on the image below.  CMC also shows installation instructions at their website found at this link.  The only significant difference in their instructions and my installation was I chose to remove the grip entirely.  Overall the basic removal and installation was very easy.

Figure 11 - Youtube Video Showing Review and Installation

These next photos show the trigger assembly installed in the upper receiver.  It is hard to tell in the photo and the video above does a better job at showing this, but the trigger assembly had some "rattle" after installed.  This was mainly because the sides of the stainless steel housing were slightly narrower that the inside of the machined area in the upper receiver.  I wasn't a huge fan of this rattle so I cut 4 plies (2 each side) of aluminum tape and placed then on each side of the assembly then installed it back into the receiver.  As I was pushing the assembly in with these additions, the tape got some wrinkles, but I was still able to push the assembly in place.  Actually I think these wrinkles helped with getting a secure fit.  Afterwards there was no rattle with the assembly.  I'm not sure if this rattle is similar for all drop in triggers, but my guess is there has to be some freeplay or the manufacturer couldn't make sure that their assembly would drop in considering the potential machining tolerances on the lower receiver slot.

Figure 12 - Trigger Assembly Installed and Cocked

Figure 13 - Trigger Assembly Installed and De-Cocked


Bottom Line:

For the $100 price I paid for this trigger on sale, the CMC AR-15/10 Curved Single State Drip-In Trigger is worth the investment.  The assembly required some basic shimming to achieve a rattle free installation, but other than that, the trigger pull measured a very crisp 3.75 pounds and should increase my ability to shoot more accurately with this rifle.  CMC makes a wide variety of triggers varying from pull weight, trigger style, stage and colors, so make sure you check them out when looking for a new trigger.

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