AR Lower-Receiver Build: Buttstock Installation

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posted on October 21, 2015
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The necessary parts and tools are listed below:

Parts
Stock
Buffer tube
Takedown pin
Takedown-pin spring
Takedown-pin detent
Buffer-tube retainer
Buffer-tube-retainer spring
Buffer (of desired length)
Buffer tube (of desired length)
Buffer spring (of desired length)
Receiver lock plate
Lock nut

Tools
Wrench for locking nut—I suggest the Brownells .223 Armorers Wrench

Insert buffer tube retainer spring and buffer tube retainer into the hole in the threaded section to the rear of the lower. For a carbine build, thread the locking nut onto the buffer tube and spin it all the way to the rear. For a rifle like mine, thread the buffer tube into the back of the receiver.

Properly installed, the buffer tube must be screwed into place, the edge of which captures the buffer-tube retainer.
For a carbine build, place the receiver lock plate over the buffer tube and thread the buffer tube into the receiver while compressing the buffer tube retainer. The buffer tube must go in enough to capture the buffer tube retainer, but not enough to bind it. (Most rifle stocks don't require use of a lock nut or receiver lock plate.)

Place the takedown pin in the receiver. Insert the detent and spring in the hole in the rear of the receiver. For a carbine build. push the receiver lock plate into place to align the buffer tube while compressing the detent spring. Now tighten the lock nut. (There are several wrenches to do this, but the Armorers wrench will also do many other functions on the AR-15 rifle and represents an excellent value. There are pre-cut locations for staking the nut to the receiver lock plate if you wish. Most, including myself, don’t bother.) For a rifle stock, simply slide it up over the tube, being sure to capture the detent and spring in the receiver as above and screw the stock into the back of the buffer tube.

Being a rifle-length build, the rear of the receiver houses the rear takedown detent and spring, which is directly held in place by the buttstock instead of a receiver lock plate found on a carbine.
Cock the hammer, depress the buffer tube retainer and insert the buffer spring, followed by the buffer. Push them in past the retainer and allow the retainer to pop up to hold them.

In his article Towsley states that he thought an adjustable buttstock is the only way to go for a home-defense carbine. For a hunting rifle like the one I’m building I believe a fixed stock to be the order of the day. Despite numerous attempts, however, I was unable to procure the stock I originally wanted for my rifle. As a result, I settled for a lightweight FAB Defense SSR25 Sniper Stock. In addition to sporting a solid length-of-pull, it also offered an adjustable comb height of eight positions  that spanned slightly more than 6 inches, which would undoubtedly come in handy in creating a sufficient cheekweld to compensate the generous height and large 50 mm objective of the I selected to mount on the rifle. To my surprise, it also contained an adjustable monopod concealed within the toe that deployed under spring tension with the simple push of a button. Each are extremely welcome feature designed to promote comfort and enhance accuracy.

The next entry will cover optics selection, and how the rifle performed on the range.

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