The Lower Receiver
I built the gun under the watchful eye of my good friend Wes Webber. Wes is a firearms instructor and armorer at a suburban sheriff's department, and he's very knowledgeable when it comes to ARs. Fortunately, he is also quite patient.

A good action block enables you to get a good grip on the receiver without marring or crushing it.

I started out by laying out all the parts for the lower on the workbench. Next, I compared my parts to the diagram and parts list DPMS provided with the kit. When I verified that all the parts were present, I started putting it together.

First, I taped the raised portion on the left side of the receiver, which contains the offside of the magazine catch to keep from scratching it before inserting the magazine catch from the left side of the receiver. Then, I put the magazine-catch spring on the catch and screwed the magazine release onto the threaded portion of the magazine catch. After giving it a few turns, I pushed it in with my punch and turned the magazine catch clockwise. I stopped when the post fit flush in the magazine release.

The bolt catch was the next bugaboo. Installing it was pretty straightforward, but the challenge was doing it without marring the receiver. I know two tricks to make it painless. Unfortunately, I didn't think to use either.

The indexing detent on the upper receiver is shown here, and the corresponding pin on the barrel is also clearly visible.

One way to install the bolt catch without marring the finish is to tape the receiver just behind the catch and tap in the pin with a roll-pin punch. That's how I did it, but I forgot the tape. Consequently, I have a few little marks on my receiver that I wish weren't there.

Once the barrel is in place, the handguard is threaded onto the upper receiver to approximately 30 ft-lbs. The gas tube hole in the handguard must match up with the one in the receiver, so make sure they are properly aligned.

To avoid this, use an old trick a buddy taught me--press the pin in with pliers. To do it, wrap the jaws of a set of Vise Grip pliers with tape and adjust them so they barely hold the pin lengthwise with the handles together. Then hold the roll pin in place on the receiver with needle-nose pliers (a little lubricant helps a lot here), open the Vice Grips, and place one jaw on the end of the pin and the other on the protrusion on the receiver. Twist the handle of the Vise Grips a turn or two at a time so the pin slides through the holes in both the receiver and the bolt catch. With the pin almost seated, a few gentle taps with a mallet--don't forget to tape the receiver--will drive it all the way home and leave the finish unmarred. Many of the AR's pins can be pressed in this fashion, resulting in a gun that looks new, as opposed to the rode-hard, put-up-wet look that's all too common among hobbyist-built rifles.

Without the right tool, the pivot-pin assembly is, in my opinion, the hardest part to install on the whole rifle. I have a tool, but I left it on the counter when I drove an hour to Webber's house to assemble the rifle. So I had to monkey with it for half an hour to get the pin in place.

With the installation tool, it's simply a matter of inserting the tool, sliding the spring and detent into the receiver, compressing the detent pin with a punch, and rotating the tool. Once everything is in place, insert the pivot pin from the other side and slowly rotate it until the detent is in the groove and push it in to push out the tool. Without the tool, it's a matter of luck, manual dexterity, and lots of bad words. Buy the tool.