by Rob Kay and RN Price

The trick is to keep this baby in while you’re trying get the Forward Takeout Pin installed. Good luck! (Watch the video)

In the last column we began the actual build of the lower receivers.  Let’s continue where we left off.

Placing the Front Pivot Pin

There are a number of ways to do this.  I think the Cheaper than Dirt folks (see video) did a good job. They used an allen wrench to keep the detent at bay. The way we did it (using a hobby knife to hold down the detent) certainly worked, but if your knife slips, the detent goes flying across the room into oblivion. These tiny suckers can be hard to find.  As the video depicts, just drop in the spring and force the detent into the orifice behind the spring with the pliers. It’s best to use needle nosed pliers to insert the detent.  Don’t even bother to try with your fingers. Make sure, if only one end of the detent is tapered, to orient that end away from the spring.

If you’re really worried about parts flying into the great abyss, both Brownells and Wheeler Engineering offer special pivot pin installation tools. While you’re in the market for tools, you’ll also want to pick up a AR combo type wrench to tighten up the buffer tube nut and the barrel.  Wheeler Engineering has a AR combo tool if you can find it in stock.

If you’re going to do this drill on a regular basis, you’ll want to pick these items for your home armorer’s kit.

http://www.youtube.com/watch?v=jp9lbQiUn4s

Installing the Fire Control Group 

This looks a little tricky but it’s not all that hard. First off, you’ll need to install the large spring on the trigger.  You’ll fumble a bit at first figuring how to place the spring but you’ll figure it out by looking at the photo on the right.
Then place the disconnetor atop the trigger.  (This is the part that looks like it has a large dorsal fin).  Note rectangular the cut at the bottom of the disconnector. This is where the top of the spring goes. Then place the other large spring to the hammer. Drop the trigger in the receiver and line it up with a punch from the left side. From the right side pop in the trigger pin and align it with the hole in the assembly and the disconnector, which needs to be depressed so the pin will “catch” it. Tap the pin in gently.
Dropping trigger assembly into lower receiver

Next you’ll need to add the hammer assembly. I had difficulty doing this.  The spring is quite strong but as always, there’s a technique. Just make sure you keep to receiver immobile as you lay down the two hammer springs and align the hole (once again with a punch) so that you can pop in the hammer pin from the right side of the receiver. Tap it and bingo, you’re there.

http://www.youtube.com/watch?v=OPomHJtqotU

Installation of the Safety Selector Lever 

This is usually a routine procedure. All you need to do is pop the Safety Lever into the receiver, drop a spring into the grip and then place the Safety Selector detent (at right) into the lower receiver. You then add the grip, making sure the Safety Selector detent spring is aligned with the hole (you placed the detent in).

Then simply screw in a screw to fasten the grip. This process went fine with the CMMG and the Stag receivers.  However, when it got time to do the same installation with the Franklin lower, there was a problem. The detent got  stuck in the channel. It has to move freely in order to engage the selector lever. To attempt to solve this issue, I took a drill bit and spun it with my fingers to try and dislodge any burrs or whatever might be obstructing things. This didn’t help. It was simply too big or perhaps the channel was too small.

Dave, the head of sales at Franklin Armory, said that they had received some LPK parts that were out of spec and surmised the detent was the culprit. He suggested gently sanding the edge of the flat “bottom” of the detent around the edges to provide more space. I sanded and over the course of an hour tried again and again to get the part to fit properly. I must have tried half a dozen times. It always seemed to stick. After a certain point (and obviously too much sanding) the part was irredeemable. Dave at Franklin responded by sending three selector detents.

This is where you pop in the selector detent (photo by Rob Kay)For good measure I also ordered one from  in Windham, Maine–a company that has great service.

For good measure I also ordered one from Windham Weaponry in Windham, Maine–a company that has great service.

One of the parts was bound to work.

One out of the three did in fact work, but not without some coaxing. The safety did move at first so I took off the grip and turned the lever so that it was able to brush against the detent without the force of the spring. After a few back and forth movements between “safe” and “fire”I put the grip back on and it was able to move the selector.

Mission accomplished.
 
Rear take down pin
The last act is to install the rear take down pin and the buffer tube.First thread the castle nut onto the buffer tube. (Castle nut cut-outs should be facing down, towards the rear of the tube). Then place the receiver end plate over the buffer tube. (Make sure the protruded little bump on the end plate is facing out. It should end up oriented towards the lower receiver, when the buffer tube is screwed int place, where it will fit into a corresponding hole in the rear of the lower receiver. Screw in the buffer tube a couple of turns. You don’t want to go too far because you’re going to need room for the buffer retainer.

Buffer tube holds the (nippled) buffer retainer in place (photo by RN Price)Next, pop the retainer over the spring and drop it in the hole in the receiver. Now turn the retainer while simultaneously holding down the retainer, until it holds the detent in place. Note that you don’t want to touch the center part of the pin and impede its movement. Insert the take down pin detent and then the takedown detent spring. Then tighten the stock in place over the spring. If you cock the hammer back (set the safety selector to “on” so that you don’t inadvertently drop the hammer), it will be easier to do. You’re going to need a special wrench to tighten the castle nut. Wheeler Engineering makes a reasonably priced combo wrench that can be used for this task. Once you tighten the nut, you’re done.

Next, pop the retainer over the spring and drop it in the hole in the receiver. Now turn the retainer while simultaneously holding down the retainer, until it holds the detent in place. Note that you don’t want to touch the center part of the pin and impede its movement. Insert the take down pin detent and then the takedown detent spring. Then tighten the stock in place over the spring. If you cock the hammer back (set the safety selector to “on” so that you don’t inadvertently drop the hammer), it will be easier to do. You’re going to need a special wrench to tighten the castle nut. Wheeler Engineering makes a reasonably priced combo wrench that can be used for this task. Once you tighten the nut, you’re done.

http://www.youtube.com/watch?v=bpsQqZIKHPs

Postscript

Given that we had parts kits from different manufacturers, we tried a modest experiment. We wondered how the Stag LPK would fit on the CMMG and vice versa. We weren’t expecting any problems–after all these items are built to spec and presumably most of the manufacturers by parts from OEMs who supply everyone. Our hunch was correct, everything fit splendidly. The only issue we had with any of the parts was with the aforementioned Selector detent from Franklin. As mentioned above, that problem was rectified with a new part.

We needed buffer tubes for this build and ended up with units from several different manufacturers–Stag, Vltor and Palmetto State Armory . All fit correctly with no installation problems. The buffer tube from Palmetto State Armory was the only one I had to order separately. (It didn’t come with a lower or with the buttstock). It was one of the only companies that seemed to have buffer tubes in stock. I was very happy with both the product and their service. It was sent to me in about a week, which was pretty amazing considering the current environment.

CMMG with CTR stock

Many thanks again to Windham Weaponry, which produces some well-reviewed rifleand, sells a comprehensive selection of AR parts. They are great to deal with. Thanks also to Franklin Armory, CMMG and Stag Arms for their cooperation in helping us put together this story.

All three companies make very fine rifles.

As an added reference to building an AR 15 we suggest you look at Brownells, which has an excellent series of videos an other learning resources.  Here’s a good place to start: http://www.brownells.com/.aspx/lid=11011/learn/

We’re not finished yet. In our next article we’ll look at the completed lowers in detail and take them out to the range.

Stay tuned.

Questions?  Comments?  Contact us directly at ontargethawaii@gmail.com

Rob Kay writes about firearms for Hawaii Reporter and is the author of How to Buy an AK-47.
 
Read more of Rob’s articles on OnTargetHawaii.com

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