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AR-15 Build - Our CHQ Cabin Fever Project Part 2, Step 3, Completion Of The Lower Receiver

AR Stocks
Sorry for the long delay between Part 2, Step 2 and Step 3, the completion of your AR-15 lower receiver, but ending these abusive blanket shutdowns and getting America back to work is our top priority, 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 collapsible stock assembly, which consists of the rear takedown pin, buffer retainer pin, buffer tube, buffer, the stock and their associated springs and detents. Here’s a diagram of the whole assembly from Brownell’s.

We have used mil-spec collapsible buttstocks from KAK Industry and on our long-range rifles the EX Performance Adjustable Stock from Adaptive Tactical, both install the same and get 5-stars from us.

To keep things simple we are going to assume the use of the KAK mil-spec collapsible stock that is already mounted to the buffer tube because there is no reason to remove the stock to install the assembly on your lower.

Our KAK stock came with a red plastic cap screwed to the buffer tube that retained the buffer and spring inside the tube. Carefully unscrew the plastic cap and remove the spring and buffer, remember they will be under strong spring tension, and set them aside.

Next unscrew the “castle nut” (part #9 in the Brownell’s diagram) and remove it and the backplate, the backplate is part #7 in the diagram. Take a good look at the back plate it has a slight circular protrusion or boss that fits into a corresponding circular inlet in the butt-end of your lower.

Screw the castle nut back on the buffer tube with the large notches trailing, or pointing toward the butt stock, then slide the backplate on to the buffer tube.

Now is when you are going to wish you had three hands but persevere – it’s not that hard.

First, inserting it from right to left, place the rear takedown pin in its lug hole, making sure the grooved side is oriented toward the butt-end of the lower. Use a big piece of masking tape or duct tape to hold it in place so you don’t have to worry about it falling out while you do the rest of the assembly.

Next, insert the buffer retainer pin spring in its recess in the threads in the buffer tube attachment ring at the butt-end of your lower. Put some high-temperature gun grease in the recess when you insert the spring and place the buffer retainer pin over the spring and press it down a couple of times to make sure it moves freely in the recess. The buffer retainer pin and spring are parts 1 and 2 in the Anderson diagram you should have printed out at the beginning of this process.

Now, get the buffer tube assembly started in the threads. A little Blue Loctite on the threads of the lower is a good idea but be careful to keep it away from the buffer retainer pin and spring.

Back the castle nut and backplate well up the threads and screw the buffer tube assembly into the lower, push the pin down with your screwdriver and screw the tube in until it captures the edge of the retaining pin body. It should not be up against the pin itself, just needs to go over the edge of the body to keep it from escaping its recess.

Once the buffer tube has captured the edge of the buffer retainer pin body insert the rear takedown pin detent (part #3) in the small hole in the rear of your lower and then place the spring (part #4) in the hole after the detent.

Important Note: Looking at the Anderson diagram you might think the detent goes in on top of the spring, it doesn’t! The detent goes in first, then the spring goes on top of the detent to tension the detent into the groove in the takedown pin and retain the pin.

At this point you will observe that the spring sticks out well above the surface of the lower; stop and visualize how the rest of the parts fit together. You may also want to get your dry cleaning bag ready, because those springs have been known to launch into the distant corners of the galaxy never to be seen again if you lose control of it while under tension.

Using your piece of old credit card or other thin flat surface carefully push the rear takedown detent spring down into the hole until it is flush with the surface of the lower and hold it there, being careful not to put a kink in the spring, or to let it go flying.

Slide the backplate down the buffer tube until it is snug on top of whatever you are using to hold the spring in and then pressing down firmly on the backplate pull out whatever you are using to  retain the spring and push the backplate home with its circular boss registering in the corresponding inlet in the rear of the lower.

Keep holding that backplate firmly against the receiver until you have completed the next step!

This all sounds very complicated but if you look the parts over carefully and visualize how they will fit together before you start it will work smoothly and working inside your dry cleaning bag will minimize the chances of losing a small part like the takedown pin detent or spring.

Now you are ready to screw the castle nut firmly against the backplate. Keep pressing the backplate hard against the receiver, put a little Blue Loctite in the treads and screw the castle nut hand tight.

At this point it is handy to have an AR armorer’s wrench with pins that fit in the notches or crenellations in the castle nut so that you can snug it down really tight. Absent a proper armorer’s wrench, you can use a strap wrench or even a punch inserted in the notches and carefully tapped until the nut is tight.

You are now ready for the final operation in the assembly of your lower, insertion of the buffer and spring into the buffer tube.

Using your six-buck long shank screwdriver depress the buffer retainer pin and feed the buffer spring and buffer into the buffer tube. The spring goes in first, then the buffer goes in with the sort of torpedo shaped end going into the spring. One of the wide quadrants of the flat end of the buffer should rest against the buffer retaining pin. Once you have the buffer captured behind the retaining pin push it back and forth a few times with your finger to make sure the buffer is seated in the spring and that it moves freely and does not hang up.

You can now remove the tape from the rear takedown pin, and if you bought one of the kits with a pre-assembled upper receiver from Palmetto State, Stag Arms, Del-Ton, Anderson, Brownell’s or Midway you are ready to put the two halves of your rifle together and function test it.

If you do not have a pre-assembled upper you are going to have to take a break and spend a little time or money getting the right tools together to correctly assemble your upper receiver, but that’s our next column: AR-15 Build - Our CHQ Cabin Fever Project Part 3, Step 1, Upper Receiver Tools And Small Parts

Miss Part 1? Here’s a link.

Miss Part 2, Step 1? Here’s a link.

Miss Part 2, Step 2? 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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