Throwback Thursday: Configuring an AR-15

Cheaper Than Dirt-branded AR-15 lower receiver

One of the virtues of the AR platform is its modular design. You can customize the AR-15 in literally thousands of different configurations. The wide array of choices however can leave many new to the AR platform perplexed with just where to begin.

So where do you begin? Regardless if you just picked up a new rifle at the gun store or you plan to build your own—you need a plan. Let’s start with the lower receiver and go from there.

Lower Receivers

I’m not going to go into great detail of choosing which brand of lower to buy. There are literally hundreds of manufacturers out there. It seems that everyone and their brother make an AR lower these days, and the quality of construction varies widely.

The generally accepted top manufacturers for AR lowers are Continental Machine and Tool (CMT), Lewis Machine and Tool (LMT) and LAR Manufacturing. All of these manufacturers turn out lowers for a number of other manufacturers. CMT, for example, makes lowers for Stag Arms, Rock River Arms, Colt, Smith & Wesson and Wilson Tactical among others. LMT makes AR lowers for Lauer, DS Arms, Armalite, Knights Armament and Barrett. LAR supplies lowers to Bushmaster, DPMS, CMMG, and Fulton Armory.

This list is by no means exhaustive. Any lower purchased from any of these manufacturers will be a quality piece. I’m not saying that there aren’t smaller outfits that also produce quality parts; definitely do your due diligence when choosing a lower from a small manufacturer.

Lower Parts Kits

If you are building a rifle from a stripped lower, the first thing you need to do is get a lower parts kit. Unless you are building a custom match-grade target rifle, the DPMS lower parts kit is a great kit and includes all the parts you need to put together your lower, including a pistol grip.

One extra part you may need is an ambidextrous safety selector. This little part is a must-have for lefties. If you are building a match rifle, you may consider a CMC drop in trigger over your rifle’s stock trigger. The CMC trigger gives you a much shorter trigger pull with a light and crisp break.

For more about lower receivers and lower parts kits, read these articles


Next, you will want to put a stock on the lower receiver. For a traditional look, you can always go with the tried and true A2-style fixed stock, although many like the adjustability of a six-position adjustable stock. If you’re a smaller person, you will probably want to go with a six-position stock since you can adjust the length of the pull to suit you personally. The Leapers M4 collapsible six-position stock is a great bargain and includes the necessary aluminum buffer tube and spring as well as a sling swivel.

For more about AR-15 stocks read AR Replacement-Stock Options

Upper Receivers

Now it’s time to turn our attention to the upper. Building your own upper can be a daunting task, and is not something that everyone has the tools or capability to do. That being said, you may want to be extra picky in choosing your complete upper, as many options are available depending on the primary role your rifle will have. There are many choices you can make here. Do you want a 16-inch barrel, or a longer 20-inch barrel? What about the handguard? Should you stick with the traditional two-piece, or go for the tactical free-floating quad rail? What about a carry handle and flash hider? The answers to all of these questions depend largely on the role you want the rifle to play and your budget.

For more about AR-15 upper receivers, read Bolt-Carrier Assembly: The Heart of an AR-15.

Gas Systems

When building or selecting an upper, you have the choice of using a traditional direct impingement gas system or going with one of the new gas piston uppers. Traditional direct impingement systems divert some of the hot expanding gas through the gas tube and back onto the bolt, pushing it back and ejecting the spent cartridge. Piston systems work by having the gas push a piston and rod, which in turn push the bolt back. Because the piston seals off the gas from the bolt, piston systems tend to stay much cleaner than direct impingement systems. Gas piston systems are available in kit form or as a complete upper.

For more about gas systems read these articles


If you are building a match-grade target rifle, you may want a longer barrel—20 inches or more. You may also consider getting a barrel with a 1:7 twist to stabilize heavier bullets. Forearm rails will likely be unimportant since you probably won’t want to hang a bunch of heavy accessories off the barrel of your target rifle. Alternatively, you may want to go with a flat top upper. You can also go with a carbon fiber foregrip to save weight. For someone building a tactical response or 3-Gun rifle, a shorter 16-inch barrel with a 1:9 twist and a threaded muzzle for a flash hider makes the most sense.

For more about barrels read these articles

Handguards and Rails

If your budget allows, a free float quad rail from Daniel Defense, Troy Industries, or Yankee Hill will provide plenty of room to mount accessories and a sling. Free float rails are favored for their accuracy. A sling attached to a rifle without a free float tube can actually pull the barrel off line when slung tightly.

Free float tubes allow you to pull the sling tight, flexing only the tube and not the barrel. If you do decide to go with a free float rail system, you will need to replace your front sight—if your barrel has one—with a low-profile gas block that will allow the quad rail to fit over the gas system. Additionally, quick-detach Picatinny sling mounts are available for mounting a sling to your free floating quad rail.

If you need something a bit cheaper, there are some very good budget options like the Leapers UTG Quad Rail Forearm or the Tapco Intrafuse handguards. Complete uppers like the Yankee Hill Specter Black Diamond carbine represent the top of the line in tactical grade components. The Specter Black Diamond has a free floating machined aluminum quad rail with diamond cutouts.

Flat Top V. Carry Handle

A flat top receiver allows the most customization for your setup, though some people still prefer the carry handle. You can mount optics on your carry handle using a number of quick-detach handle-mounted rails, but if you’re going to frequently be using optics, a flat top allows for better sight height. If you can’t decide whether to go with a flat top upper or a carry handle upper, you can always split the difference and get a AR-15 detachable carry handle. This carry handle contains an A2 rear sight system, and can be quickly attached or removed from your flat top upper. If you go the flat top route, and are building a carbine for close quarter’s battle (CQB), you may want to look at a flip-up rear sight and red dot combo. Flip up rear sights allow you to use either the red dot or the iron sights, and can even be set up so that the iron sights co-witness with the red dot.


Magazines can be very confusing to someone who is gathering accessories for their first AR. What’s with all the different colored followers? Should you spend the extra dough on Magpul Pmags? Why go with polymer instead of the traditional steel USGI magazines? Both polymer and steel mags have their own advantages and disadvantages. Which one you choose depends on your individual needs as well as your budget.

U.S. military surplus steel magazines are abundant and cheap, and spare parts are easy to find for them. On the downside, they can develop rust and are prone to being dented and crushed. Polymer magazines never rust (though their springs can), but over time they can chip and crack. Some even develop cracks down the spine, rendering them inoperable.

AR magazines and their various colored followers have seen numerous upgrades throughout the years. Most milsurp magazines have green followers, but the military is now transitioning to its current model of tan followers. Be careful when shopping for magazines, as many commercial grade manufacturers have followers in a variety of colors. For commercial magazines, follower color does not have the same significance as it does for military surplus magazines. One example of currently available US military surplus magazines is our Bushmaster 30 round magazine. These are made by a variety of government contractors, so the markings on them may vary, but they all meet military specifications and have green followers.

Surplus military AR magazines are cheap and plentiful, but many people swear by Magpul PMAG polymer magazines. PMAGs have been around for a while, and early on earned a reputation as a “bulletproof” magazine that is virtually indestructible. PMAGs are also supremely reliable. They are available with and without a clear plastic window, which allows the shooter to quickly and easily see how many rounds are left with just a quick glance.

Many people complain about how difficult it can be to cram 30 rounds into an AR magazine, but you don’t have to hurt your thumbs getting all of those rounds into your mag. Cammenga manufactures a 30 round magazine they call the EasyMag. The EasyMag opens up for easy loading that won’t bruise your fingers. Someone in the military liked it so much they actually purchased a number, giving the EasyMag its own NSN. The ones we sell are not military surplus, but they are identical to the ones issued to the military.

For more about AR mags read these articles


Discussing rail-mounted accessories is opening up a huge can of worms. Suffice to say, if you can imagine it, someone has figured out a way to mount it on a Picatinny rail. The most common accessories are flashlights, forward vertical grips, and laser systems. You can even get a light, laser and a vertical foregrip as a single unit, saving you valuable rail space. I could go on and on about the thousands of rail mounted accessories, but the beauty of the modular AR quick detach rail system is that you can quickly and easily install and remove whatever accessories you want.

In fact, one of the primary reasons for the success of the AR platform is its modularity. With one lower and a handful of uppers or parts, you can go from a short-barreled 9mm carbine to a .22 Long Rifle plinker to a match-grade .223 rifle all in the same day. No matter what type of rifle you need, you can build an AR to accomplish the task. It’s the Swiss Army Knife of rifles.

For more on accessorizing your AR-15 read these articles

There are so many ways to customize your AR-15. What have you tried? What are your favorite customizations? Tell us in the comment section.

This article originally published on February 1, 2011.

The Mission of Cheaper Than Dirt!'s blog, The Shooter's Log, is to provide information—not opinions—to our customers and the shooting community. We want you, our readers, to be able to make informed decisions. The information provided here does not represent the views of Cheaper Than Dirt!

Comments (12)

  1. Great Article. ideas . I loved the information – Does anyone know where I might acquire a sample FL DoR DR-15CS document to edit ?

  2. AR-15 is one of the most accessorized rifle in the world. Even if it is not yet customized it’s already looking good. How much more if you put accessories on it.

  3. One nifty AR accessory I’ve learned to appreciate is the extended Bolt Catch / Release. This allows a shooter to manipulate the bolt release lever using their trigger finger without ever having to take it out of the trigger guard.

    With an extended release installed, there is no need to ever have to release the bolt with your non-shooting hand ever again. They are easy to install and go over your existing release lever paddle with a single tightening of a screw.

    The two most popular models are sold by Troy and Magpul. Troy calls theirs the “Troy AR-15 Ambidextrous Bolt Release” whereas Magpul calls theirs the “Magpul B.A.D. Lever (Battery Assist Device)”.

    Here is a video comparing the two:

    And here are CTD links on pricing:


  4. I know the subject is AR. But on my LR I used the LaRue RAT stock. A DPMS Panther grip with large heel. ALG Defense ACT trigger/hammer assembly. Heavy Buffers spring/buffer.ARES Armor AJAX .308/18 in. barrel. Magpul MBUS Pro 45 degree offset hard sights. Topped off with a Primary Arms 4-14×44 FFP scope. All on a Aero Precision M5 lower…

  5. After making several mods to my AR, there’s one thing that AR’s must have. I can’t live without my CAA UPG16! It’s one of the most overlooked accessories there is.Command Arms has what I think is the best replacement there is. It comes with front and back inserts that give total control of the weapon. I can actually do one-handed(not recommend) maneuvering, with total control of the weapon like a pistol! While firing, my hand fits in the finger grooves and the palm swell like it was molded for me. That cheap, hard, slippery and hard to grip peice of junk that ships with most AR’s really needs to be the first thing for the trash!

  6. One accessory I CAN’T be without is my damn magazine lock! Thank you Kalifornia! Seriously, though, I’m not big on ‘accessorizing’ my ARs, but I did run a DD free float quad rail on my heavy barrel varmint AR for 2 reasons: More barrel exposed to help keep the barrel cool and to help keep weight down. Just saying… BTW, working on a tactical ipad case that will mount to my pic rail. It’ll have a swivel on it so I can turn it to see the screen and be able to record my shooting, or see my ballistics plotting (kind of like a digital range card)… Going to mount it opposite my cup holder! Patent pending!

  7. LMT does not make lower receivers for Knight’s Armament Company and has not for some years now. KAC produces all of their lowers for the SR-15, SR-16, and SR-25 at their Titusville facility.

  8. Two other advantages with installing a multi-position stock:

    1 – If your rifle will be used by multiple shooters, such as a family gun or a training gun, you can quickly adjust the rifle to fit the shooter.

    2 – If you anticipate using your rifle in a variety of clothing situations – wearing body-armor one day, a t-shirt the next, body-armor over a parka the next. Training and weapon-familiarity are important so that you know what stock-setting to use to accomplish your mission no matter what gear you are wearing.

  9. Not only did I purchase a spec ops collapsible stock for my M4 I also bought a Tapco infusion rail system, a saw style pistol grip for my big hands a surefire rail mounted weapons light, but also a Trijicon A.C.O.G with back up iron sights on the A.C.O.G. The Short barrel I prefer because I used to do a lot of urban combat practice.

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