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AR-15 Build - Our CHQ Cabin Fever Project Part 2, Step1 Lower Receiver Assembly

AR 15 Assembly Part 2
Before we start on the actual assembly of our AR-15 lower we will answer the most pressing question about our tool list: What’s the dry cleaning bag for?

One of the most frustrating things about assembling an AR-platform rifle is the number of small springs and detents that can be launched across the room during the assembly process never to be found again. This is a distinct possibility if you don’t have some of the specialized tools designed to keep that from happening. Working a few of the assembly jobs inside the dry cleaning bag will limit the flight path of those errant parts and increase the likelihood that you will find them if you do launch them. Sounds crazy, but it works.

Also, if you haven’t yet “caught your rabbit” and found an AR-15 lower at your local gun shop, the nice folks at Ready Gunner have some available as of our post time.

Editors Note: We have no affiliation with any of the suppliers mentioned in this article and receive no benefit, freebies or compensation from any of them.

Before you start your build go over this lower parts list from the nice people at Cheaper Than Dirt to make sure you have all the parts you need. You should also check to make sure all the holes and recesses are clear of debris from the machining process and that all the threaded parts are sharp and screw together properly. We once received an LPK that had one part that had not been tapped. Needless to say, it was impossible to screw that part and its mate together, the good news is we sent it back and the manufacturer made it right, but it was a pain and held things up.

You can also print-out this diagram and parts list from Anderson Manufacturing to help you identify the parts and follow along as we describe how to assemble them into a working AR-15 lower receiver.

The first thing we always do is install the trigger guard. Typically, the “front” will have a spring-loaded pin already installed and the “back” is the end with a hole all the way through. The holes go up and the flat or curved side of the trigger guard goes down, retract the pin with your fingernail or knife tip and slide it into the bracket right behind the magazine well. If you have it positioned correctly the pin will pop into the hole. Next retract the trigger guard into the rear bracket and position it so the holes in the bracket line-up with the holes in the trigger guard and prepare to insert the roll pin.

Roll pins are an invention of the Devil designed to tempt you to take the Lord’s name in vain.

To avoid that temptation put a drop or two of gun oil in the hole and chamfer one end of the roll pin with a file or sandpaper or as a last resort, give one end a series of squeezes with your pliers to reduce the diameter and allow you to get it started in the hole. Be sure not to flatten the roll pin if you decide to give it a squeeze, work all the way around it squeezing as you go to keep it round and don’t succumb to the temptation to drill out the hole to make it bigger; there is not a lot of material there and you could leave your gun fatally weakened or even break the “ear” of the trigger guard bracket.

Use a block of wood or a deck of cards to make yourself a block to support the “ears” and gently tap the roll pin through the pre-lubed trigger guard. In an ideal world you would have what is called a “roll pin starter punch” if you don’t have one use needle nosed pliers to hold your roll pin until it is well started and for the last few taps you might want to protect the finish of your gun with some painter’s tape.

There’s also a specialized punch for getting the ends of the roll pin countersunk below the surface of the “ears.” If you don’t have one you can make one out of a nail – just be careful not to bash the “ear” of the trigger guard, they are surprisingly fragile for a military grade gun.

Next, we install the magazine catch assembly. This is straightforward but needs to be done in the correct sequence: Insert the mag catch into the recess on the left side of the receiver with the shaft going through the hole to the right side of the gun.

Insert the mag catch spring into its recess on the right side of the receiver, making sure the shaft of the mag catch goes through the spring. Line up the mag catch button in its recess, with the crosshatched side up, and press the mag catch button down until you can engage the threads on the shaft. This takes a little two-handed coordination to push and turn at the same time.

Once you get it started get it lined-up correctly and push the button all the way down with a dowel – I use an old fashioned basic Bic pen, one of the handiest gunsmithing tools ever invented – and turn the mag catch assembly to screw it in until it just clears the left side of the receiver. You may have to adjust it a little to make sure it firmly catches the magazine and is comfortable for your finger to use the release button, back it off a turn if the shaft comes out the top of the button.

Next, is the bolt catch or bolt stop assembly. Again, the first steps are simple, but you must do them in the correct order. First, place a piece of painter’s tape on the left side of your receiver to protect the anodizing, then start the roll pin by using a punch or long shaft hex head screwdriver to tap it into the hole, just a couple of taps will do because you don’t want to block the recess where the bolt catch level sits.

Next, put a drop of gun grease in the bolt catch hole on the left side of the receiver, then drop the spring in, then the bolt catch plunger. The plunger is a funny looking little part with a bulb and a short shaft – the shaft goes down into the recess (hole) on/in the top of the spring, the bulb points out – check to make sure it moves smoothly in and out.

Next place the bolt catch on top of the plunger and prepare to drive the roll pin through the hole in the bolt catch lever. This one is intimidating but don’t be put off by its odd positioning.

In an ideal world you would have a special punch that is flat on one side to use for this job, but if you don’t you can use your interchangeable long shaft screwdriver. Use one of the hex heads of your long shaft screwdriver as a punch and tap the roll pin home.

I know your Dad and Granddad told you never to use a screwdriver this way, but this is one of the MacGyver workarounds for those operating in a tool-poor environment. You can get a 10-piece set of interchangeable blade screwdrivers with long shafts from Home Depot, yes they are cheap Chinese junk, but you won’t feel bad if you use one as a punch because they only cost about seven bucks and my set has lasted for years.

The final step in this part of our build is installation of the front take down or pivot pin.

So, you might want to get your dry cleaning bag ready, because this is one of the steps in our AR-15 lower receiver build that has the potential to launch small parts into the next room. This is also the time to dig out one of those fake credit cards the Bank of Vigorish sends you to try to induce you to accept one of their pre-approved 36 percent per month interest credit cards. Your pivot pin is about 1.25 inches long, cut a strip about ¼ to ½ inch wide off one end of the card before running the rest of the card through your shredder. The purpose of this little piece of plastic is to protect your finger and give you a flat surface to push the detent flat and lay the pivot pin on while sliding the pin into the bracket or lug.

The easiest way to do this is to buy the special tool to take care of this job (only $10 to $15), but we are working in a tool-poor environment. Some builders prefer using a knife in place of a piece of credit card or other thin plastic. I’ve used a one-sided razorblade too but using anything with a blade adds an element of unneeded danger to the process, so before I bought my installation tool, and after launching three detents in one build, I figured out the dry cleaning bag and credit card MacGyver.

Take a look at the front (muzzle) end of your lower receiver. Note that in front of the magazine well there are two brackets or lugs with holes through which the pivot pin slides, and on the right side is a small hole for the pivot pin detent and spring. You are going to slide the pivot pin in from the right, over the detent and into the right lug.

First, put a drop of gun grease in the pivot pin detent hole on the right front of the receiver. Put the grease in now because hopefully you will never see that hole again.

Next insert the detent spring in the hole. If you are worried about launching and losing parts, now is the time to put both hands and the receiver in the clear plastic dry cleaning bag.

Place the detent, the little brass torpedo-shaped part, on top of the spring and use the flat side of your piece of credit card to depress and hold the detent down until it is fully retracted in the hole, then hold it there!

This is not easy, it is definitely a two-handed job to keep the parts lined-up and depress them flat, but working inside the clear plastic dry cleaning bag should reduce the worry about launching and losing these little parts.

Starting on the right side of the receiver, while holding the detent in captivity with your piece of credit card, slide the pivot pin across the piece of credit card and into the right pivot pin lug or bracket. Once the pivot pin is started in the bracket you can withdraw the piece of credit card because the pivot pin will now retain the detent. If you withdraw the piece of plastic before the pin covers the detent it will definitely launch, so take it slow and make sure you have the pivot pin covering the detent and started in the lug before you pull the piece of credit card out. Once you withdraw the piece of credit card the detent will be captured in the groove in the pivot pin and retain the pin in place pretty much forever.

There, you are now ready to install the fire control system, but that’s our next installment: Part 2, Step 2, Installing the AR-15 Fire Control System.

Miss Part 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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