This is it. The last few pieces. In the grand scheme of things, final assembly is probably the least involved aspect of building an AR-15, but it is the point where this pile-o-parts finally takes shape as a true usable weapon.
Let’s see here, what do we have?
Constructed Lower Receiver
Constructed Upper Receiver
Bolt Carrier Group
There’s really not much to this part, is there? Since I already talked in-depth about the Upper and Lower receivers, and sights or optics are worthy of significant posts of their own, let’s focus on those last two parts. The Charging handle is fairly self explanatory. It is the handle that you use when charging the rifle for the first time after loading in a new magazine. It’s actually a very seldom used device, thanks to the semi-automatic nature of the gun itself. It’s just a piece of metal (or sometimes even plastic), roughly T shaped, that you grab and pull rearward like the plunger of a pinball machine to load in your first live round. It always has some kind of latching mechanism on it, to keep it from flying rearward when firing the weapon, but the form that takes is often variable. Mine comes from Strike Industries in the guise of their Extended Latch Charging Handle. It’s an all-aluminum model (most have steel latching mechanisms) designed to reduce wear where it contacts the aluminum of your receiver. The extended latch handle allows you to operate it just by grabbing one side, rather than both sides of the T. Many people find this to be a little easier and more natural than grabbing it in the center. I agree, finding that doing so makes it easier to use my left hand to charge the weapon without shifting grip with my right.
The Bolt Carrier Group is one of the largest and most complex internal parts of the AR-15. It is an intricate part of the firing mechanism, including the bolt and firing pin, but also a major component of the recoil system with the carrier. The BCG is really the “action” of an AR-15. It is the central portion, and combined with the fire control group (the BCG resets the hammer after each shot) and the recoil system (the BCG rides into the buffer tube with each shot) makes up basically the entirety of moving parts. They are available in a number of different formats such as M-16 or AR-15, plus more. These variants are sometimes called Full Auto or Semi Auto or other names as well. There’s a lot more to the story, but the gist of it is that any BCG will work in an AR-15 without altering the functionality. There are some lingering questions about the legality of using an M-16 or Full-Auto BCG in an AR-15, but since doing so without adding any other full-auto components does not allow the AR-15 to fire any more than one round per trigger pull, you should be quite safe using one without running afoul of the BATFE. Of course, I’ll include the usual disclaimer that I am not a lawyer, nor do I even play one on the internet, so you should do your own legal research on this matter. I myself feel completely comfortable in this regard.
In addition to differing weights/structures, BCGs come in a wide variety of coatings. From the basics like hard chrome or manganese phosphate (known as Parkerized) through common coatings like Nickel Boron, and up through a wide variety of specialty coatings like Titanium Nitride or others. Each has specific strengths and weaknesses that are worth studying, despite the incredible amount of feelings-based “facts” on the internet. The Bolt Carrier Group being installed into this particular rifle is one of the more space-aged new-fangled varieties. It comes from a company called Cryptic Coatings that I stumbled across during my research. I really have no idea how I ended up finding them, but I sure am glad I did. They offer a wide variety of coated BCGs in various properties. Each line also has a unique color, which aesthetically complements the differences in performance. I’m using their Mystic Bronze coated group, which statistically has the second best inherent lubricity of any of their products, as well as by far the best appearance of any BCG I’ve yet seen. Opinion, I know, but it’s my site. With the distinct prevalence of monochrome throughout the rifle, I was oh so pleased to find one piece that would provide the chromatic exception to the rule that brings the entire ensemble together. Having that color come as a result of better wear resistance, lower friction coefficient, and easier cleaning and maintenance is icing on the cake. I tend to shy away from superficial upgrades whenever possible, (excepting the muzzle device, of course, because: Dragons), preferring instead to have superior aesthetics come alongside superior performance. Hopefully the Mystic Bronze will live up to its hype. I intend to see.