Installing an FCG in AR is pretty straight forward, regardless of brand, so long as the lower is built to spec. This article shows the installation of Geiselle SSA but the procedure is the same the standard AR trigger as well.

Before starting, make sure you have a slave pin. Geiselle provides one with their trigger but it would be easy to make one from a piece of drill rod or a spare trigger or hammer pin. Also, you'll need grease. AR FCG need to be lubed with grease where the sears make contact and I apply a coat to the bottom of the hammer and each pin. Removing the FCG is easy. Just drive out the two pins with a small hammer & pin punch. I have never had to remove the safety. Make sure the safety in the "FIRE" position before disassembly & assembly.

Before starting, inspect the hammer to make sure the internal J spring is in place. It's needed to lock the hammer pin in place and keeps it from drifting out.

A note on the M&P-10- Most folks remove the right side bolt release to make it easier to install the hammer. I did not. The hammer can be installed with the release in place but it's much more difficult.

The Geiselle SSA-E came as two sub-assemblies (trigger and hammer) along with a slave pin and a small tube of grease (pin & grease not pictured). It is very important to lube any AR FCG before installation. Even a quality G trigger will have a gritty pull if not lube. Make sure the hammer sear gets a good dollop


The trigger sub-assembly came with the trigger pin installed. Remove the trigger pin and install the slave pin in it's place.


The slave pin is needed to hold the disconnecter in place, making installation of the trigger assembly much easier. Push the trigger pin out-


-and make sure the slave pin fits evenly. Note the trigger and hammer pins have two grooves cut in them, one near the end. It doesn't matter which way the grooves are facing when the pins are installed.


Place the trigger sub-assembly in the trigger housing of the lower receiver. Tip it so the tail slips under the safety. Make sure the legs of the springs point forward to rest directly on the receiver on each side of the trigger cut-out.


Press the trigger sub-assembly down until the slave pin lines up with the trigger pin hole


Now press the trigger pin into place. It will push the slave pin out the other side. The pin can be installed from either side of the receiver. The pin slid into place with just finger pressure.


Next, install the hammer. If the hammer pin is installed in the hammer, remove it. Inspect the hammer spring and make sure it's installed on the hammer correctly. The first photo shows how the spring should look.

Drop the hammer into place. The spring legs must point to the rear of the rifle and must rest on the trigger pin in the groove. This locks the pin into place so it will not drift out. Once the spring properly placed, press the hammer down until the pin hole in the hammer lines up with the hole in the lower


Start the pin into the hammer. The hammer spring will make it a little more challenging than installing the trigger, but with a little patience it's not difficult. Sometimes, using an alignment pin on the opposite side helps. In the hammer is a J spring which will fit into the center groove to lock the hammer pin in place. You might need to give the pin a light tap with a small hammer & drift to set it in place. Only tap the pin in place enough to hold hammer


Pressure from the hammer spring will keep the pin from aligning with the pin hole on the opposite side of the receiver. Turn the receiver over. Grasp the hammer, line up the holes and push the pin the rest of the way in. NOTE: If the end of the pin is pressed against the inside of the receiver, it will create enough binding that the hammer cannot be lined up. Make sure the pin isn't causing binding.


This is what the pins will look like once everything is in place


Done


Once finished, assemble the upper to the lower and test for proper function. DO NOT DRY FIRE ON AN UNASSEMBLED LOWER! The hammer striking the lower could cause damage.

Follow these instructions and you'll find installing an AR FCG a snap. Keep the slave pin. Without it, installing the reset sear is very frustrating