Ask Foghorn: What Parts Should I Use when Building an AR-15?

Many, many many readers have written in over the last couple weeks asking roughly the same thing:

I was reading your article on Best Budget AR 15 and I tried to click on the build recommended links but most don’t seem to work now. Do you have an updates? or suggestions? I am very interested in learning more and trying to build my own.

So you want to know what my build list would look like these days? Let me knock you up a list . . .

First things first, my normal recommendation for people building an AR-15 is to build the lower yourself and buy the upper receiver complete and already assembled. And I’ll be following that recommendation with my parts list.

The reason I suggest buying the upper receiver as one complete pre-assembled part is that when you start mucking with headspace and gas tubes and trying to get the proper torque with barrel nuts, there is a whole lot more that can go wrong if you don’t get it close to spec. Not even the professionals always get the proper torque on the barrel nut (which leads to decreased accuracy and in some rare cases the barrel flying apart), so expecting a new AR-15 builder to get it right on the first try might be asking too much. But with the lower receiver, there isn’t anything that will kill you or decrease accuracy if you get it wrong.

There’s also a lot more to upgrade on the lower receiver. With the upper, the only thing that you would really be tweaking are the optics and handguards. But with the lower, you can do anything from getting a new trigger to swapping out the stock. And each change makes a huge difference to how the rifle handles.

Oh, and if you don’t know how to put together an AR-15 lower receiver, I’ve got an article for that. Now for the parts list (skip to the bottom for just the list and no descriptions).

Lower Receiver

The lower receiver is the bit that holds the gun together. And, in the eyes of the ATF, it is the gun. Which means you’ll need to get yours from an FFL if there isn’t a helpful citizen available to sell you one in a “private party” transfer.

Aero Precision is my current favorite manufacturer, they make parts for Boeing aircraft and in their spare time they started precision manufacturing lower receivers. I used one of their lowers in my competition rifle, but their rollmark seems to have changed quite a bit since the early days. Heck, back then they didn’t even have a website. Next on the list is Franklin Armory, whose lower I used in my testing rifle and looks pretty cool.

The good news is that no matter who you pick, as long as they’re not some fly-by-night operation you’re fine. Lower receivers are all the same, built tot he same specs and nearly identical from one to the next in terms of everything from dimensions to metallurgy. The only difference is the rollmark and the safety selector indicators on the lower. Unless you go with a funky polymer lower, that is.

Lower Receiver Parts Kit

If you look at my article on building a lower receiver, you will quickly find that there are a ton of little pins and springs that go into one of these guns. So rather than going out and buying each pin individually, the smart move is buying the parts all in one go. DPMS’ parts kit is the best I’ve used, so long as you immediately throw out the trigger and the grip. Everything else is golden.


The trigger should be the main focus of any upgrade to your rifle. Its where you will notice the most increase in accuracy and speed for the least investment, and its one of the easier parts to swap out. I’ve been a huge fan of the ALG Defense QMS trigger, as it provides the best balance of performance and expense to the new shooter. Plus, the thing is tuned by Geissele’s people before it leaves the factory for extra awesomeness.


The grip on an AR-15 rifle is all about comfort. You need to be able to comfortably grip the gun and have your finger positioned perfectly on the trigger in order to get the most accurate shot. For that reason, I really like Magpul’s MIAD grip kit. It gives the shooter a grippy surface for better holding onto the gun, and allows them to change the shape of the grip to match their own hand. Plus, it just looks awesome.

Buffer Tube / Receiver Extension

The fiddly bit that sticks out the back of the rifle, whatever you call it, needs a little extra attention than most parts. There are two versions, the “mil spec” and the “commercial” version. The only difference is that the commercial version is slightly larger than the mil spec variety, but whichever one you choose you’ll need to make sure your stock matches up. That’s why I default to mil spec, since its less likely to be out of spec. DSA makes a complete kit that has everything you need for this section, including the rear plate, buffer spring and buffer.


Not to be a Magpul fanboy, but their stuff is the best on the market in terms of comfort and reliability. And for those on a budget, their stocks are actually pretty reasonably priced. My current go-to stock is their MOE Carbine collapsible stock, which might be a little more expensive than the standard looking stocks but makes it up in the cool factor.

Upper Receiver

For the upper receiver on my “screwing around / testing stuff” rifle I’m using a pre-ban DPMS M4-style upper (yay New York). I personally find the fixed front sight post and carbine length gas system fits my needs perfectly, and I get the feeling I’ll love it even more once I chop the barrel down. Unfortunately, those have been out of stock for quite some time. But there are alternatives out there. Like the Del-Ton upper that is nearly identical and costs a lot less (if it ever comes back in stock).

Iron Sights

Since the upper comes with a fixed front sight post, the front sight is unnecessary. However, a rear sight is a good idea if you actually want to hit anything. Magpul makes a back-up iron sight that costs around $60, but its lightweight and gets the job done. I really like it.

The List:

That comes to a total of roughly $792 before taxes and shipping, but its a rifle that has all the bells and whistles of a $1,000+ gun.

Now, keep in mind that just about everything is sold out right now thanks to the rumors of impending doom and gloom. But as soon as this all blows over, expect there to be a rather large surplus of parts. That’s the nice thing about panic buying — it saps the cash out of the suckers and creates a surplus (and therefore discounts) on the other side of the hump.

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