Thursday, January 7, 2010

Configuring an AR-15

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One of the virtues of the AR platform is its modular design, and the ability to customize it 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. There are already a number of fine articles and videos out on the internet that cover various aspects of assembling your own AR. Yet, we still get new shooters calling and emailing us confused by the wide variety of options available.

Smith & Wesson M&P 15
So where do you begin? You've got that brand new AR home from the gun store. Sure, it's fine in a stock configuration. M16s just like it served our military for decades through numerous wars and performed well in their stock configuration. Yet, there are many ways that the AR can be customized and improved upon. Maybe you just picked up a new rifle, or maybe you're going to build your own from scratch. Either way, if you're going to be building it or upgrading it, you'll want to have a plan.

I'm not going to get into the details of choosing what brand of lower to buy - there are literally hundreds of manufacturers out there. It used to be that there were only two or three manufacturers of AR lowers on the market, and they all made pretty much the same thing, so it didn't matter which brand you bought. Nowadays it seems that everyone and their brother is making an AR lower, and the quality of construction varies widely. The top manufacturers for AR lowers are generally accepted to be CMT (Continental Machine and Tool), LMT (Lewis Machine and Tool) and LAR Manufacturing. All of these manufacturers turn out lowers for a number of other manufacturers. CMT for example makes lowers for Stag, 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, but suffice to say that 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, but you should definitely do your due diligence when choosing a lower from a small manufacturer.

If you're building a rifle from a stripped lower, the first thing you'll need to do is get a lower parts kit. Here at Cheaper Than Dirt! we carry the DPMS lower parts kit. Unless you're building a custom match grade target rifle, the DPMS 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 Timney drop in trigger over the stock trigger. The Timney trigger gives you a much shorter trigger pull with a light and crisp break.

Next you'll want to throw a stock on that lower receiver. For a traditional look, you can always go with the old tried and true A2 style stock. But many people like the adjustability of a 6-position stock. If you're a smaller person, you will probably want to go with a 6-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.

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" barrel, or a longer 20" barrel? What about the foregrip? 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.

If you're building a match grade target rifle, you may want a longer barrel: 20" or more. You may also consider getting a barrel with a 1 in 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. You may however want to go with a flattop upper. You can also go with a carbon fiber foregrip to save weight. If you're looking for a complete upper for a target rifle, it's hard to do better than our DPMS LoRider. This upper has a 20 inch bull barrel machined out of 416 stainless steel with a 1 in 9 twist.

For someone building a tactical response rifle, or possibly a 3-gun rifle, a shorter 16" barrel with a 1 in 9 twist and a threaded muzzle for a flash hider makes the most sense. 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 the sling to be pulled tight, flexing only the tube and not the barrel. If you do decide to go with a free float rail system, you will need 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 option rail systems like the Leapers UTG Quad Rail Forearm or theTapco 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 cut outs. The less expensiveDPMS M4 upper is also a fine carbine length upper that is ready to go.

A flat top receiver will allow 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 be frequently 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 Mako 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 CQB, you may want to take a 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.

Yankee Hill Specter Black Diamond Upper
When building or selecting an upper, you now 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.

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 magazine have their own advantages and disadvantages. Which one you choose depends on your individual needs as well as your budget. US 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 getting 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 their 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 teflon coated 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 the green followers.

Surplus military AR magazines are cheap and plentiful, but many people swear by our Magpul PMAG polymer magazines. PMAGs have been around for a while, and early on earned a reputation as a "bullet proof" 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 aren't military surplus, but they are identical to the ones that were issued to the military.

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 .22LR 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 like the Swiss Army Knife of rifles. Too many people try to make their AR into a gun that can "do it all" - that's not quite the right way to look at it. The AR can be assembled and configured to perform well in a wide variety of applications, but you can't have it perform well in any role in a single configuration. Decide what you want to do with your AR, and build it to that spec.


  1. I am trying to decide which ar lower to buy, and which company seems to manufacture it. Please send the relevant and proper information about ar lower manufacturers.

    ar lower manufacturers

  2. Beginning long-range shooting gear recommendations anyone?
    AR-15 lower parts