Tiger McKee of tacticalwire.com writes:
For the first AR I built, back in the mid 80’s, I used a mil-type barrel wrench, torque wrench, and some old punches and hammer. This can be done, but to get it “right” – assembling a reliable, accurate, and long lasting rifle – requires knowledge and specific tools. There are books on building AR’s, or videos for the visually oriented; Brownells carries good ones. Having the proper tool for any project makes the job easy and the end results look right. Again, Brownells has what’s mandatory, some tools that will make the job easier, and a few that are good to have if you’re planning lots of AR work [complete armorers’ kit above] . . .
A barrel nut wrench is mandatory. We’ve seen quite a few AR’s come to class without the barrel nut properly torqued, which can be dangerous. I use a wrench, more like a ring, that completely surrounds the barrel (714-000-020) with six pins to engage the nut. The ring requires removing the front sight base. In my opinion it’s worth the effort, especially if you have to apply a lot more torque than the min.
The older military type units will work but with only three extensions it’s not uncommon for them to slip off the nut. (Note: Some handguard/nut designs require special wrenches for that particular combination.) To do all this work on the upper receiver you’ll need either a set of barrel jaws, to clamp the barrel in a vise, or, an “action block,” (080-000-661) a better option that clamps around the receiver.
The barrel has to be torqued to a min of about thirty-four lbs. But the nut must be positioned so the gas tube freely fits through it into the receiver to mate with the gas key on the bolt carrier. Obtaining this alignment usually requires more than the min torque.
To check alignment I use an index gauge (080-216-014) that fits into the gas key of the bolt carrier. Once installed the gas tube should actually make a rattling noise when you shake the upper assembly. This wiggle room allows the bolt carrier to slide into position smoothly without wearing the gas key or applying force to the tube. Zediker, in his “Builders Guide,” (995-000-005) states that proper alignment of the gas tube is a key to accuracy.
Once the barrel is installed you have to check headspacing, confirming chamber length with the bolt closed, in battery with the barrel. Brownells carries gauges, or if you’re not planning on doing a lot of AR work find a buddy or shop that will check spacing, which only takes a few minutes. Improper headspacing can lead to explosions, and not the funny kind.
To build an AR requires punches. You need starter punches (080-685-000), roll pin punches (230-112-105), and standard punches, like a 1/8 punch to install hammer/trigger pins. Without the right punches you can ruin pins and/or destroy a receiver.
Prior to assembling the lower receiver I prep it by checking all the holes for detents, springs, take-down pins, and hammer/trigger holes with the correct size drill bits in a pin vise, which is like a screwdriver handle for small drill bits. Even a quality receiver can end up with small obstructions in these areas that will prevent proper function. (#22 bit for safety detent hole, #23 for bolt stop plunger and hammer/trigger pins, and #40 for pivot/takedown pin detent holes.) During assembly every part should be inspected for fit and function prior to final installation.
There are a lot of other cool tools that make your work easier. I use a small nail, bent into an “L” shape to hold the bolt release, spring and detent in position while driving the pin that holds it all together. Removing this pin requires a special tool (080-216-012) that is cut on one side so you can drive the pin out without beating up the receiver.
A mag release tool (100-002-127) makes installation or removal of that part simple. A pivot pin installation tool (080-216-011) holds the detent and spring in place for installing the pin. Removing this pin is about impossible without a special tool (080-216-010).
True success with any project relies on knowing what you’re doing, and having the proper tools. The AR is no exception.
Tiger McKee is director of Shootrite Firearms Academy, located in northern Alabama. He is the author of “The Book of Two Guns,” writes for several firearms/tactical publications, and is featured on GunTalk’s DVD, Fighting With The 1911 Website: www.shootrite.org