The Lower Assembly portion of this project required the bulk of the small and hard-to-handle components, but as we move to the stock and buffer system, the processes do get easier. However, there are still small parts with springs that if not carefully attended to, could shoot your freaking eye out--so be careful! There are also a few specialized tools that will make this portion of your build a snap--they are noted throughout. It's also worth noting that this is not the final part to this series, there will be one more for the build process, and more to come after in regards to adding the right accessories.
After completing the Lower assembly, the next step is attaching the buffer and stock. This is the M5 .308 Carbine Buffer Kit at a price of $69.99. The kit comes standard with the Mil-Spec 7075-T6 Aluminum Buffer Tube, 6 position, .308 Carbine Buffer, .308 Buffer Spring, End Plate and Lock Nut—much like a castle nut. All components are built in the USA.
The Magpul MOE SL-S Carbine Stock retails for $79.95 comes in two colors and features a sleek profile, dual-side latches and waterproof battery tubes, which will store up to two CR123A lithium or AA batteries on each side. Dual-side release latch that provides easy length adjustment while remaining anti-snag, plus many more features.
Here is the buffer kit on my work bench, but you’ll also notice the Buffer Retainer Spring and the Buffer Retainer. These were included in the Base Lower Parts Kit that was discussed in Part 1 of this series. The spring and retainer will be the first parts added to the Lower Receiver before buffer tube gets installed.
The spring and retainer will go in that hole inside the threaded end of the Lower Receiver.
This is the position the spring and retainer will be in once added to the Lower Receiver.
Spring first.
Retainer on top of the spring.
Line up the End Plate, thread the Lock Nut onto the buffer tube.
Begin threading the buffer tube into the back of the Lower Receiver.
Line up the End Plate.
Continue to screw in the buffer tube while manually surprising the retainer on the spring until the buffer tube reaches this point and is lined up with the End Plate.
This wrench is included in the Wheeler AR Armorer’s Ultra Kit, which makes setting the Lock Nut a piece of cake. Again, this kit is simply irreplaceable if you’re building an AR.
The wrench fits perfectly into the notches on the Lock Nut and helps the builder secure it squarely in place to lock in the buffer tube.
Here is the view of the stock assembly from the underside and do your best to line everything up so the Magpul stock will fit on there correctly.
Next will be the .308 Carbine Buffer Spring and .308 Carbine Buffer.
The spring slides in easily.
Hold the retainer down while pushing in the spring until it reaches this position. Be careful or it could shoot out of there and pop you in the chops. (Don’t ask me how I know this.)
The Buffer slides in the same way and stops at the same place. Easy.
I picked up this Masterforce Drive Bit Set from Menards for less than $30. Not only does it have unique bits and tips that will come in handy for this project, but you’ll find lots of other uses around the house or with other builds. Worth it.
If you plan on customizing from this platform, make sure you understand the necessary specs and the differences. Read this thing.
Grab the correlating torque bit to match this screw, and you’ll need to remove this one to take off the stock extension tabs on both sides.
One screw will allow for both sides to be removed.
After the tabs are removed, you’ll find this little rod sticking out, you’re going to want to remove this so you can pull the component down so the stock will fit onto the buffer tube.
A small pair of needle-nose pliers were handy for this job.
This pick and small flathead screwdriver were also key in pulling the spring-loaded component down so the stock will slide onto the buffer tube.
I won’t pretend to know what that part is called, but it’s spring loaded and I was able to push it down with the screw driver and hold it down with the pick.
Then slide the stock onto the buffer tube, all the while keeping the pick in this position. Then you can replace the pin.
Replace the tabs.
Then replace the rubber butt stop.
Now the Lower is fully assembled. The job is over halfway completed. That means it’s time to order the next project, this is a ton of fun and very satisfying.
Tom Harrison is lifelong Midwesterner and a 25-year veteran angler, whitetail and turkey hunter. His experience extends from the bass rich waters of Mexico well into northern Canada, he's successfully hunted turkeys in 13 states, whitetails in five states and one Canadian province. Harrison has been producing instructional content, speaking at tradeshows and outdoor talk radio/podcasts and creating videos for two decades regarding both the hunting and fishing in an undying effort to help others be the best they can be in the outdoors. His overall goal is to make success commonplace on the water or in the woods through hard work and a strong desire to learn.
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