How to Replace An AR Trigger

No rifle—no matter how good it is otherwise—can ever live up to its accuracy potential if it has a poor trigger. A good trigger allows the shooter to make the shot without moving the gun off target. A hard, rough trigger pull makes it much more likely to introduce negative influences that can move the rifle off target as the shot breaks or as the bullet is traveling down the barrel. A light, crisp, predictable trigger will let you break the shot with little or no impact on the rifle. Luckily, the AR style rifle and carbine is the ultimate kit gun. A do-it-yourselfer can modify just about every aspect of the gun with a few simple tools, and the single best thing you can do for most of the guns out there is replace the trigger.
There are a lot of drop in triggers on the market today, and replacing that creepy, crawly, heavy trigger with a nice clean-breaking trigger with a light pull weight that will improve the performance of your rifle beyond your expectations. As with any project, the first step is to make certain the gun is unloaded.
The trigger in an AR rifle can be complicated and difficult to adjust or tune. Replacing it with a self-contained trigger (shown outside the receiver here for clarity) solves that problem. Aftermarket trigger group assemblies for an AR-15 start at around $100 and run up to more than three times that. They're available at Brownells and other gun parts suppliers.
There are several good self-contained triggers on the market. Timney...
AR Gold...
... and Velocity Trigger are three that I have used and can recommend. Make sure you buy a model trigger that fits your rifle. Many replacement triggers will not work with some Colt rifles.
Separate the upper and lower receivers. Remove the grip from the lower receiver. Go through the bottom with a screwdriver or properly sized wrench and unscrew the bolt. The bolt is visible through the bottom of the grip and it should be easy to see the type of head to determine the correct tool. Be very careful to not lose the spring and safety detent, as they are held in place by the grip. Note the spring in the top of the grip in the photo.
Use a straight punch to push out the two pins holding the trigger parts in place.
Then remove all the trigger parts and the safety lever, which is sometimes called the fire control selector. (It's much easier to work if the gun is held solidly in place, so place a Brownells lower receiver vise block into the magazine well and clamp it in your bench vise.)
Clean the receiver with a degreasing spray to remove all dirt and debris.
Insert the new trigger into the receiver and place the rear pin through the holes. It sometimes helps to use a slave pin to hold everything in alignment while starting the pin. Insert the safety and then insert the front pin. Replace the grip, making sure to put the detent and spring into the hole in the receiver. This step is easier if you turn the receiver upside down.
Follow the instructions supplied with your specific trigger. Most triggers use set screws to hold the assembly in place. Tighten each screw against the bottom of the receiver, alternating back and forth a couple of times to make sure they are tight. Some, like the Timney, use a second locking screw. With any screw, I like to add a drop of blue Loctite to the threads on each one.
Check that the trigger is functioning properly by cocking it and pulling the trigger several times. I like to use a Brownells hammer drop block for dry firing. You can get by without it by catching the hammer on your finger, but don't let the hammer impact the lower receiver over and over because doing so can damage the receiver. Check that the disconnect is working. Pull the trigger and hold it back. Cock the hammer and then slowly release the trigger; you should hear and see the disconnect release. There should be a click and the hammer will move forward slightly. If that checks out, test the safety. Cock the hammer, put the safety to the “on” position and pull the trigger several times. Don’t be afraid to pull it hard. If nothing happens, push the safety off and make sure the sear does not release. Put the rifle back together. Make sure that it’s not loaded, the hammer is cocked and the safety is off. Thump the buttstock on the ground soundly several times. The hammer should remain cocked.
The new trigger should have a much lower pull weight, a much cleaner feel, and make your AR-15 a sharper-shooting rifle. Bryce M. Towsley is the author of “Gunsmithing Made Easy,” which details numerous gunsmithing projects. It is available at brycetowsley.com.