How to Install a Fire Control Group Upgrade in your AR

Unless you are that person most of us know someone who is really frugal. Someone who doesn’t see the value in a $150+ FCG upgrade. Maybe that viewpoint is correct. The notion inspired yours truly to see if its possible to get a substantial performance improvement out of low-cost FCG upgrades- without polishing any surfaces. Details on the ALG combat trigger upgrade shown in this post are in this breakdown of different FCG options.

Installing an upgraded Fire Control Group (FCG) in your AR platform rilfe can appear daunting- particularly if you haven’t built a lower before. Reading this post should demonstrate how easy it is and hopefully will motivate you to give it a try. You will only need a few items to complete this upgrade: a new FCG, electrical tape, punch set and light hammer. You also may need some heavy duty grease if your FCG didn’t arrive pre-lubed. You also may want to use a wood block or vise to help with trigger pin installation.

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 1. Never deviate from safe firearms handling protocols. Unload the rifle and ensure it is safe. Remove all ammunition from your work area. Remove the upper receiver from your rifle and put it aside. You may want to remove the stock from the rifle – it’s your choice but is a nice way to keep the stock from getting dinged up.

2. You may want to remove the safety lever from the lower. It’s an extra step but it can make the process easier.  Back out the screw from inside the pistol grip and carefully remove the grip (slowly enough to not lose the spring and detent that are pressing into the safety lever. Once this is complete the safety lever will slide out easily.

3. If you didn’t release the hammer before you removed the upper do so now (aka press the trigger- but read the next sentence first). Be careful to hold your thumb over the hammer and let it release slowly to prevent it from striking the bolt catch. Now apply electrical tape over the trigger pins on the lower. Don’t be shy about tape coverage unless you like scratches and marks on your lower.  

4. These pins hold the FCG together and be advised that the right pin is holding the disconnector in place and you will want to apply a little pressure from the top as you drift the pin out to prevent the disconnector from flying out of the receiver as it’s under spring tension. Start with the left pin and remove the hammer. Now drift out the right pin and remove the trigger and disconnector.

Here are the two FCGs side by side. At a glance the only difference seems to be the ALG’s NiB finish and the shape of the disconnectors. However when weighing the  comparative parts I discovered that the ALG trigger was 30gr lighter than the shite stock trigger that I couldn’t wait to remove.

5. You may have to install the springs on your components. In this case the good people at ALG took care of that before the FCG was packaged. Be certain to double check springs before you go forward. This thread is full of pictures of proper spring positions. Now is the time to verify that your trigger bores are lubed up- this will help installing the pin easier. Now install the trigger and disconnector into the lower receiver. Holding the disconnector down to align the holes in it and the trigger with the lower (right side in photo shown in step 3)  trigger pin hole, install the shorter of the two pins you received with the FCG. 

You can probably accomplish this without using the punch or hammer but it should only take a few light taps if there is resistance.  You could also use a pliers if you prefer but be sure to tape the ends of the pliers with electrical tape to avoid marring or bending the pin. When this is complete your lower receiver will resemble this one:

6. Now reinstall the safety lever if you removed it in step 2. No need to replace the pistol grip assembly yet, just make sure the safety lever is in place (it can and will spin around)

7. Now for the hammer. Place a drop of lubricant in the hammer pivot. Install the hammer with the spring legs on top of the trigger pin grooves. Press the hammer into the receiver and install the other pin through the receiver, through the hammer and secure in the other side of the receiver. Once again only light force should be required to install the pin- just be sure to visually confirm the hole alignment and it should be a simple task. Remove the electrical tape and admire your work:

7. Ensure the FCG is lubricated according to manufacturer guidelines. This will help the FCG operate smoothly. 

8. Reinstall the pistol grip and safety detent assembly. Also reinstall the stock if you removed it.

9. Reinstall the upper and function check the rifle. Pay close attention to the safety and trigger reset.

10. Enjoy the satisfaction that performing your own rifle upgrade can provide.  All that work and it took filler to get to 10 steps! As easy as advertised, don’t you think?

 

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