Most people fail to understand that an AR-15 often gets a lot of use. In fact, it is not uncommon for one of these rifles to cycle as many rounds in one day as some other guns will see in a lifetime of use– perhaps even in several lifetimes of use. The practical outcome of this is that an AR-15 is subject to more wear-and-tear on its internal parts and also needs to be kept rigorously clean to extend its service life to the greatest extent possible.
While it is common to disassemble and clean the bolt carrier of an AR, the same care is sometimes not applied to cleaning AR-15 lower receiver groups. Gravity decrees that dirt and powder residue are likely to congregate down in the crevices of the bottom of the receiver, which is a pretty good reason to pay special attention to it.
For this discussion, the AR-15 lower parts kit essentially consists of three separate modules: the selector, the trigger assembly, and the hammer group. To truly get the rifle clean, you need to swab out the bottom of the receiver well where the fire control parts are installed. This can’t be done while they are in position, so they will have to be removed.
Start by removing the selector lever as the first step in taking out the AR-15 lower parts kit. This is held in place by a tiny pin that sits underneath it, which is held in place by a long spring that fits into the top of the pistol grip. Remove the screw that holds the pistol grip to the receiver and is careful not to lose the spring or the little metal pin that sits on top of the spring. Once these are out of the way, the selector lever will come right out.
Some rifles, particularly newer models, feature anti-walk pins to hold the trigger and hammer in place. These can be identified by the small c-clips on each side of the pin that protrudes beyond the frame of the receiver. Popping one of the clips lose allows you to withdraw the assembly with ease, but watch out for flying springs.
For older rifles, things have to be done in a little more organized fashion. You will need to start with the rolled pin that holds the hammer in place. Push it to one side or the other with the point of a bullet or some other thin, pointed object and then wiggle it loose– being careful not to bend it or burr up the surface of the pin. Once it is out of the way, the hammer and its spring can be removed. Because of the way in which the hammer spring is employed to secure the trigger pin, it is necessary to remove the hammer first and trigger group afterwards. Conversely, the trigger group goes back in first upon reassembly.
Once everything is out of the way, you can scrub and lube everything and then put it all back together. The advantage of doing a complete takedown is that cleaning AR-15 lower receiver groups on a regular basis allows you to keep an eye on whether they are showing any signs of increasing wear. Unless you continuously view your parts groupings, you have no baseline case against which to compare them once they do start to wear.
So a full cleaning not only extends the life of the parts you already have but also, allows you to track changes in them so that you will know when the time comes to replace the entire group with a new AR-15 lower parts kit. Always replace your parts in sets rather than by swapping out individual pieces, always keep your gun clean, and always use high-quality ammunition. That way you will always hit your target when you need to.