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AR-15 Build - Our CHQ Cabin Fever Project Part 2, Step 2, The Fire Control Group

AR 15 Assembly Part 2
Sorry for the long delay between Part 2, Step 1 and Step 2, but there’s been a lot of Democrat craziness going on out there (and some Republican craziness too) so we had to address that before getting back to our AR-15 build.

Just to recap – we’ve got our AR-15 lower receiver ready to accept the fire control group, which consists of the trigger, hammer and safety selector and their associated springs and detents.

The first thing you should do is lay out the parts and get a good look at them before doing a test fitting. Here’s a link to a picture of the parts for the trigger and hammer assembly.

In an ideal world you would have or make what is called a “slave pin” to hold the trigger assembly together while you insert the trigger pin into the receiver. You can make a slave pin out of a nail, 5/32 rod stock or a spare trigger pin if you have one – it should be 5/32 (.154”) in diameter and 5/8 or 16mm long. If you don’t have anything you can cut down to that length, be prepared to have some patience for the assembly of your trigger.

Note that the little disconnect spring has a top and a bottom orientation, it is important to assemble the trigger with this spring correctly orientated for your trigger to work. The larger end of the spring will fit into a little circular recess in the channel in the top side of the trigger body.

If you printed-out this diagram and parts list from Anderson Manufacturing the trigger spring is Part #26; it is the spring with the shorter “legs” to distinguish it from the hammer spring. Pop it over the pin bosses on each side of the trigger body with the two “legs” of the spring pointing forward and the U-shaped section of the spring under the “beak” or prow-shaped front of the trigger body. Make sure it seats in the grooves on each boss.

Place the disconnector spring (larger end down) in the little circular recess, if your trigger body has two circular recesses use the front one, and then place the disconnect or disconnector (Part 28) in the trigger body channel with the notch in the bottom of the disconnector over the disconnector spring and the hole lined-up with the trigger pin holes in the trigger body. You may need to give the assembly a firm squeeze to ensure the disconnector spring is fully seated in its little recess and the hole in the disconnector lines up with the pin holes in the trigger body, rock it back and forth a little to make sure it works smoothly.

Now, in our ideal world you would put a dab of grease in each hole, slip the slave pin into the hole in the right side of the trigger body, through the hole in the disconnect and into the hole in the boss on the left side and leave it there holding the trigger assembly together.

You could then place the trigger assembly in your lower receiver (with the beak or front of the trigger body pointing toward the magazine well), and with the ungrooved end first, get your trigger pin started in the hole in the right side of the receiver and line up the holes and following the slave pin, push or gently tap the trigger pin through the five holes in the receiver, disconnect and trigger body.

If you don’t have a slave pin, but you do have a 5/32 drill bit or punch, you can use that in lieu of a slave pin to help you line everything up. Insert the shank of the drill bit or the punch in the left side receiver hole, carefully work it through the five holes in the trigger assembly and receiver, and then push or tap your trigger pin from right to left with the ungrooved end first. The drill bit or punch will give you more leverage and material to hold on to and help you keep everything lined up as you push or tap the pin the through the five holes it needs to pass through to hold the trigger assembly in place.

Note: use the shank, not the cutting end of your drill bit to avoid damaging the finish on your receiver.

If none of these tools are available then simply work your trigger pin through the five holes, starting with the ungrooved end on the right side of the receiver. If you still have your little piece of plastic or old credit card you can use that to protect the thumb or finger you are using to apply pressure to the trigger pin while you manipulate the trigger body and disconnector with your other hand.

Getting all five holes lined-up is not rocket science, but it does require a little patience – I’ve had pins go through on the first push, other times it has taken what seemed like forever to get the job done; just relax and work the pin across one hole at a time.

Once you have successfully installed the trigger check to make sure the legs of the spring are tight against the receiver and release the trigger and rock it back and forth to make sure it works smoothly. Don’t pull the trigger and let it bash into your receiver, just release it a few times to make sure it is not hanging up for some reason.

Next is the installation of the hammer and spring.

Before you install the hammer take a good look at it paying particular attention to the pin hole. You will note that there is what looks like a wire in the hole – that’s the “J spring.” If it is not there you need to stop and get another hammer, because the J spring is what locks the hammer to the hammer pin’s central groove.

Before you install the hammer, put a dab of grease in the pin hole to help reduce friction and potential damage to the J spring when you tap the pin through.

Pop the hammer spring on to the bosses so that it is oriented like this. The best way to describe the correct orientation is you want the U-shaped section of the spring to snap on to the body of the hammer and rest against it at angle pointing back toward the trigger body – if it is standing straight up it is probably on backwards.

Get your hammer pin started in the receiver, again working from right to left starting with the ungrooved end of the pin.

Place the the legs of the hammer spring on top of the trigger body bosses and push the assembly down until the holes in the hammer bosses line-up with the holes in the receiver and push or tap the pin into the hole in the right boss of the hammer.

Note: The hammer spring is quite strong, so it will take a considerable amount of force to hold it down and allow alignment of the hole and pin. Having your piece of plastic or old credit card will protect your finger or thumb while you are pushing on the pin to get it started. Once it is in the boss you can push it or gently tap it through to the other side.

You will meet some resistance when the pin gets to the J spring, so getting it past the J spring will require a firmer push or tap, but don’t bash it with your hammer! If you greased it the pin will slide through with only modest persuasion.

Check to make sure the legs of the hammer spring are resting on top of the trigger pin bosses, and then push the pin through the left side of the receiver. Looking at your lower receiver from the right side, when you are done you should see something like this. Hammer configurations vary, so yours may not look exactly like this, but you should get the picture.

Perform a function test by cocking the hammer back and engaging the disconnector. Be sure to hold the hammer when you release the trigger – don’t let it bash the receiver or bolt catch as the hammer falls with enough force to damage either of those parts.

Our final assembly in this section is installation of the safety selector; this is part 24 in the Anderson Manufacturing diagram.

Insert the safety selector in the hole in the left side of the receiver – you may have to work in back and forth a little and it helps to grease the shaft before inserting it. Orient it so the pointer is in the “up” or “fire” position.

Hold the selector in place and turn your receiver over, next to the tab for the pistol grip you will notice a small hole, this is where the safety selector detent goes. Put a drop of grease on the hole and insert the safety selector detent. This is part 6 in your Anderson Manufacturing diagram – looks like a little tiny bullet, insert it into the hole with the pointy end first. Make sure you keep the selector in place, if you take it out the detent will fall out and bound into the deepest darkest crevice in your floor never to be seen again.

Next, insert the safety selector detent spring (part 7) into the small hole in the top of the pistol grip and slide the pistol grip over the tab, making sure the spring enters the detent hole.

Remember that six buck long shaft screwdriver? Find the correct hex head to fit your pistol grip screw, mine is marked H3-16, but yours may vary.

Put the washers over the screw and insert the screw and tighten it, being careful to get it tight without stripping it.

You are now ready to function test the fire control group. Select “safe” (pointer toward the front or muzzle of the rifle) and depress the trigger. If you did everything right the trigger won’t move. Now you can select “fire” (pointer pointing straight up) and, being careful to hold the hammer so it does not fall on the bolt catch or receiver, depress the trigger – if you did everything right the hammer will fall and you are ready for Step 3 – installation of the buffer tube, stock and rear take down pin, but that’s our next column, so check back later this week for the next installment of Our CHQ Cabin Fever Project AR-15 Build.

Miss Part 1? Here’s a link.

Miss Part 2, Step 1? Here’s a link.

CHQ Editor George Rasley is a certified rifle and pistol instructor, a Glock ® certified pistol armorer and a veteran of over 300 political campaigns, including every Republican presidential campaign from 1976 to 2008. He served as lead advance representative for Governor Sarah Palin in 2008 and has served as a staff member, consultant or advance representative for some of America's most recognized conservative Republican political figures, including President Ronald Reagan and Jack Kemp. He served in policy and communications positions on the House and Senate staff, and during the George H.W. Bush administration he served on the White House staff of Vice President Dan Quayle.

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