Smith & Wesson M&P 40 Trigger Kit Installation

The Smith & Wesson M&P 40 handgun in this article had along trigger travel (7/16") followed by a 7.8 pound pull that released the striker after another 1/16" of travel. This is typical of older striker fired handguns. Gun manufacturers have improved the triggers on newer models. I have a Ruger LCP II that has a much better trigger than the original LCP. Aftermarket suppliers have seen the opportunity and offer kits to improve the trigger action on various makes and models.

One of those is Apex Tactical Specialties (Apex- Tactical.com, They offer trigger kits for the S&W M&P and Shield models. I installed the Apex M&P Aluminum Forward Set Sear and Trigger Kit. The kit includes an aluminum trigger with the safety blade in the face of the trigger; a striker block, spring, and installation tool; four and five pound trigger springs; sear and spring; and a slave pin for installing the trigger pin.

This kit is designed to reduce the overall trigger travel by about 50% and reduce the pull to approximately four or five pounds. Installation I removed the magazine and made sure the chamber was empty. I removed the slide, then removed the recoil spring assembly and barrel, and installed the slide in a vise with padded jaws. The rear sight must be removed to access the striker block and spring. Before staring, I marked the location of the sight on the slide to maintain the zero.

The set screw in the sight has a 1/16" hex head and thread locker that makes it difficult to remove. If you’re not careful, the screw hex can be rounded out (if the wrench doesn’t yield first) and we know where that leads. Heat is required to soften the thread locker. I did not want to put an open flame on the sight so I used the following method. I installed the longest 1/16" hex head wrench that I had, with the shorter leg in the screw and the longer leg pointed away from the slide.

The nozzle of a heat gun was held against the longer leg so the wrench could conduct the heat into the screw. I used a pair of pliers at the corner of the wrench to apply torque. After several minutes, I was able to remove the screw with little effort. I wasn’t sure that the heat gun would work Far

but it did and it didn’t overheat the wrench. After the screw was removed, the sight was drifted left to right to uncover the thin washer underneath. This washer sets on top of the spring and striker block. The kit has a tool that fits in the dovetail on the slide and is used to contain the washer and spring when the sight is removed and installed. The original spring and striker block are removed and replaced with the new parts.

The new striker block has a larger radius that reduces the friction when lifted by the trigger bar. The new striker block spring is shorter which reduces the force to move the block. I checked the bore in which the block is seated to make sure there wasn’t anything that would prevent it from moving freely. The washer is installed and held in with the tool while the sight is installed. After the sight was realigned with the slide, the set screw was installed with low strength thread locker.

The rest of the new parts are installed in the frame. The two roll pins are pushed out from either side with a 1/8" punch. The trigger pin is pushed out, from right to left; it has ahead on the left end. The takedown lever is removed by tipping it up and pulling to get it past the retaining wire in the locking block. Remove the locking block, making sure the takedown lever retaining wire doesn’t fall off and disappear. Lift out the slide lock lever and trigger and trigger bar assembly.

The sear housing fits tightly in the frame and is gently pried up to remove it. The ejector sets on the left side of the sear housing but does not need to be removed. The sear is retained by a small pin and is pushed out (right to left on this gun) with a punch that re- Below center: Removing sear pin with punch. tains the sear when the pin is out. Hold the sear in place while removing the punch. The sear, plunger, and spring are removed.

The new spring, the plunger, and the new sear are installed and held in place with the punch acting as a slave pin while the sear pin is installed. The trigger bar is removed from the trigger by pushing out the pin on the trigger (right to left) far enough to allow the trigger bar to be removed. The new trigger has the pin installed part way and it must be pressed in to capture the trigger bar. Apex recommends putting the trigger in a vise and closing the jaws to push in the pin.

There is a video on their website that shows the procedure. After trying unsuccessfully to tap the pin in while holding the trigger bar, I used their method. I put the trigger in a vise with smooth jaw plates. The new trigger has a V-shaped relief on the

right side where the trigger bar is installed. I found that putting the trigger in the vise with the Vslot pointed straight down helped align the trigger bar. The end of the trigger bar is pushed to the bottom of the slot in the trigger and that aligns the hole with the pin. Make sure the trigger bar is oriented correctly; the trigger spring tang should be pointed to the left side of the trigger.

Tightening the vise slowly pushes the pin toward The trigger spring in the side lock lever for installation in the frame. The new trigger total travel is 1/8" and the pull weight is 4.2 pounds. the slot. Take your time and check to see if the bar is captured by the pin. It took a fair amount of force to move the pin. After the pin has started into the bar, push it the rest of the way. The new trigger spring (small end) is hooked on the trigger bar tang and the other end slid into the trigger.

I used the 4 pound spring. The trigger is installed in the slide lock lever and the slave pin is used to keep the parts aligned during installation in the frame. The locking block is installed in the frame, making sure that the takedown lever retaining wire is in place. The trigger pin is installed, left to right, driving the slave pin out the right side. The sear housing is slid into the frame, pushing it forward and downward, making sure the end of the trigger bar goes under the sear.

The two roll pins and takedown lever are installed and the slide assembly is installed. A function check was performed and it showed that the trigger, sear and trigger safety were operating correctly. This handgun does not have a manual safety. The new trigger location is where the original trigger stopped after its initial 7/16" of travel and the new trigger pull is 4.2 pounds (compared to the original 7.8 pounds) with only 1/8" total travel. The trigger has a short, positive reset.

This trigger kit reduced the trigger travel by about 75% and the pull weight by about 50%, making the pistol easier to shoot accurately. It was well worth the investment. AG