Featured AR-10 Lower Receiver Buyer’s Guide Tyler Elsberry May 6, 2022 Join the Conversation THE AR-10 LOWER RECEIVER IS NOT AS STANDARDIZED AS THE AR-15’S, BUT THIS GUIDE SHOULD HELP YOU KEEP THE VARIANTS STRAIGHT AS YOU DIVE INTO BUILDING YOUR OWN. OUR AR-10 LOWER RECEIVER PICKS: PSA GEN 3 PA-10 STRIPPED LOWER NEW FRONTIER ARMORY G-10 BILLET LOWER (GEN 2) STAG ARMS STAG 10 STRIPPED LOWER RECEIVER AERO PRECISION M5 (.308) STRIPPED LOWER RECEIVER ARMALITE AR-10 A-SERIES STRIPPED LOWER RECEIVER RAINIER ARMS ULTRAMATCH .308/7.62 MOD 3 BILLET AMBI LOWER RECEIVER WHAT MAKES THE AR-10 PROPRIETARY: Unlike the AR-15, AR-10s do not have standardized parts and components. AR-15s benefit from mil-spec parts and components due to the adoption and further development of Eugene Stoner’s designs by the U.S. military. The AR-10 saw no widespread adoption by the military so there is no common mil-spec standard, but rather various patterns that have their own quirks and compatibility concerns. Due to the difference in scale, many AR-15 parts and components will not work with AR-10s. Particularly, the variance of receiver thickness on AR-10s mean components such as magazine release assemblies and takedown/pivot pins do not have widespread compatibility with AR-10s. This may warrant the purchase of a specific AR-10 parts kit. For example, Aero Precision’s M5 lower parts kit includes proprietary components such as an extended magazine release button to compensate for the thicker receiver. There are some more obvious incompatibilities with AR-15 parts and components as well. Large-frame ARs will not accept AR-15 handguards. Barrels from AR-15s also are a no-go with AR-10s. Muzzle devices common to AR-15s are also incompatible with AR-10s due to the different thread pitch and bore diameter. Fortunately, there is no need to borrow AR-15 parts for your AR-10 project and the latter is just as easy to assemble as its smaller cousin. There are heaps of AR-10 specific parts and components available. Handguards, barrels and muzzle devices specifically intended for AR-10s are plentiful on the market. One just needs to be aware of the various patterns and their compatibility with different parts and components. THE DOMINANT AR-10 PATTERNS: The most prolific AR-10 patterns on the market are the DPMS Gen 1 and Armalite patterns. Other patterns exist, but they are less prevalent and more proprietary. Accordingly, we will focus on the DPMS and Armalite AR-10 patterns. Armalite pattern lower (top) vs. DPMS pattern lower from PSA (bottom). DPMS pattern AR-10s can be identified by the curved cut where the receivers meet. The curvature of the DPMS pattern cut is reminiscent of the standard receiver cut present on most AR-15s. Generally, DPMS pattern lower receivers have an integral trigger guard, often in the oversized “winter” style to accommodate gloves. Most of the AR-10 parts and components on the market adhere to the DPMS pattern. There are two major variations on the DPMS pattern: the low receiver and high receiver variants. Accessories are made for both styles, but this is something to keep an eye on to make sure everything is compatible. Confusingly, while DPMS was under the Remington umbrella, they introduced a Gen II version of their upper and lower receivers which was smaller and lighter than the Gen I, but this didn't make as much headway in the market and is currently out of production. Armalite originally developed both the AR-10 and AR-15. The “AR” prefix in both of these firearms refers to “Armalite Rifle.” An Armalite pattern AR-10 can be identified by the sharp angular cut where the receivers meet. Armalite pattern lowers typically are compatible with mil-spec trigger guards. While not as common as the DPMS pattern, it should be noted that a variety of MIL/LE oriented companies such as Lewis Machine and Tool and Knights Armament Company utilize the Armalite pattern in their large-frame ARs. It goes without saying that DPMS and Armalite receivers are incompatible with each other. The geometry simply doesn’t match up. Major parts and components besides receivers are specified as either DPMS or Armalite pattern compatible and consumers should take care to be sure of what they are buying. Like building an AR-15, it makes a lot of sense to just buy major AR-10 components from the same manufacturer to ensure compatibility. WHAT ISN’T PROPRIETARY: Just because AR-10s are incompatible with most AR-15 parts doesn’t mean there isn’t some overlap in components. Here are some of the components that are generally compatible with both AR-10s and AR-15s. MAGAZINE RELEASES: Most AR-10 lower receivers will accept standard magazine release assemblies. Some lowers are thicker than others and a standard magazine release button may be too short in some cases. Some AR-10 receivers are specifically marketed as being compatible with popular ambidextrous magazine releases such as those made by Norgon. Some accessories such as the Magpul Enhanced AR Magazine Release are marketed as being “compatible with most 5.56 and 7.62 pattern receivers” but there is no guarantee due to the wide variety of lowers on the market. Norgon ambi mag release. TRIGGER GROUPS: Mil-spec style trigger groups will generally fit into AR-10s as easily as they do AR-15s. Fire control groups from manufacturers such as Geissele Automatics and LaRue Tactical will be at home in an AR-10 build. SAFETY SELECTORS: For the most part, AR-10s will accommodate mil-spec safety selectors. Some AR-10 lower receivers are specifically marketed as being compatible with ambidextrous safety selectors like those from Battle Arms Development and Radian Weapons. MOST LOWER PARTS KIT COMPONENTS: While we already addressed the compatibility of magazine release assemblies, trigger groups, and safety selectors, we have not addressed the litany of small components that come in lower parts kits. For the most part, the various pins and springs found in lower parts kits will work with AR-10s. For example, the Aero Precision M5 lower parts kit only comes with three M5 specific parts: the magazine release, a pivot pin, and bolt catch. The rest of the included small parts are no different from those found in standard lower parts kits. BUFFER TUBES AND BUTTSTOCKS: AR-10s are compatible with many buffer tube assemblies on the market. Carbine and fixed buffer tubes are common sights on many AR-10s. Any number of stocks can be affixed to either of these kinds of buffer tubes. Everything from B5 SOPMODs to classic A2 fixed stocks. More exotic options are also compatible with AR-10s such as the Magpul UBR Gen 2, a stock that features a proprietary buffer tube. U.S. Marine Maj. Gen. Douglas V. O'Dell shoots a KAC SR-25 AR-10 with a fixed-stock. GAS BLOCKS AND GAS TUBES: Most of the gas blocks and gas tubes on the market will work with AR-10s. Front sight posts, low-profile, and adjustable gas blocks alike will work on an AR-10 build. Whether building an AR-10 or AR-15, attention must be paid to barrel diameter and gas block size. A barrel with a diameter of .750 inches simply will not accommodate a gas block with a diameter of .625 inches. PISTOL GRIPS: Almost all AR-15 pistol grips are compatible with AR-10s. Due to potential differences in geometry, there may be a gap between the receiver and tang of the pistol grip depending on the lower and grip chosen. Some receivers, such as Aero Precision’s M5 lower, are marketed as eliminating this gap. Whether you want a standard A2 grip or something like Magpul’s K2 grip, either will work on an AR-10. 6 TOP AR-10 LOWER RECEIVER OPTIONS: PSA GEN 3 PA-10 STRIPPED LOWER: Palmetto State Armory, a brand known for its affordable AR-15s and components, also dabbles in AR-10s. Their Gen 3 PA-10 lower receiver is an economical option for those wishing to build an AR-10. The PA-10 adheres to the DPMS pattern and can take advantage of a vast array of parts and components. The Gen 3 update to the PA-10 lower added the benefit of increased compatibility with more AR-10 bolt carrier groups. Palmetto State Armory runs frequent sales, allowing for this receiver and other necessary components to be purchased for even cheaper. With a PA-10 lower receiver, one can start an AR-10 build project that won’t break the bank. MSRP: $149.99 // palmettostatearmory.com NEW FRONTIER ARMORY G-10 BILLET LOWER (GEN 2): The New Frontier Armory G-10 lower is another affordable option for those wanting to get into AR-10s. The G-10 is a DPMS pattern billet lower receiver , allowing it to accept most AR-10 parts and components on the market. A threaded bolt catch pin eliminates the need for a roll pin and makes installation easy. The G-10 also features a receiver tension screw that eliminates slop between the upper and lower receivers. All in all, the G-10 lower is good value and includes many desirable features at a sub-$200 price point that is easy on your wallet. MSRP: $169.99 // newfrontierarmory.com STAG ARMS STAG 10 STRIPPED LOWER RECEIVER: While many AR-10 lower receivers feature integral trigger guards, the Stag 10 is compatible with any mil-spec style trigger guard. Prospective purchasers should know that the Stag 10 follows the Armalite pattern, so other parts should be chosen accordingly. It should also be noted that Stag Arms is a company known for manufacturing AR-style rifles for left-handed shooters, so if you want to build a left-handed AR-10 the Stag 10 left-handed upper options would be a solid choice too. The Stag 10 stripped lower receiver allows you to get into an Armalite pattern AR-10 for less than $200. MSRP: $174.99 // stagarms.com AERO PRECISION M5 (.308) STRIPPED LOWER RECEIVER: Aero Precision is a well-known manufacturer of economically priced and high-quality firearms, parts, and components. Their foray into the realm of AR-10s comes in the form of the M5. The DPMS patterned lower receiver sports added creature comforts such as a threaded bolt catch pin and tensioning screw. One can also consider Aero Precision a one-stop-shop for the major parts and components of their M5. Everything needed to complete the build can be acquired from the same place the lower receiver is sourced. Aero Precision also runs frequent sales on their site, making it possible to pick up an M5 lower receiver and things like lower parts kits for a better price. Aero Precision has long represented both great value and quality in the black rifle market; the M5 is no exception and will serve you well. MSRP: $204.99 // aeroprecisionusa.com ARMALITE AR-10 A-SERIES STRIPPED LOWER RECEIVER: If it weren’t for Eugene Stoner and Armalite, the AR-10 and AR-15 wouldn’t exist. The company has produced a myriad of high-quality firearms throughout its existence, thus cementing the brand as a household name. It’s only natural that they have continued to manufacture AR-10s into the present. Building an AR-10 from Armalite components comes with the added cool factor of being able to claim ownership of the real McCoy (even if the Armalite of today isn't exactly the same company as the one that originally spawned Stoner's designs). The Armalite A-Series lower is also compatible with mil-spec trigger guards, allowing further customization of a build. While this lower is more expensive than some other options, the appeal of owning an actual Armalite rifle and the overall quality make this a worthy consideration for an AR-10 build. MSRP: $227 // armalite.com RAINIER ARMS ULTRAMATCH .308/7.62 MOD 3 BILLET AMBI LOWER RECEIVER: The UltraMatch lower receiver from Rainier Arms includes proprietary ambidextrous controls. These ambidextrous controls are certainly a creature comfort and an enhancement to general ergonomics. While the UltraMatch lower receiver appears to possess the traditional DPMS style receiver cut, Rainier Arms states that it “may not fit most upper receivers” and recommends it be paired with their UltraMatch billet upper receiver. The billet nature of the UltraMatch upper and lower receivers should also be noted, as it is typically best to pair billet receivers together rather than mix and match. The UltraMatch lower receiver from Rainier Arms provides both premium aesthetics and features that would make an excellent base for an AR-10 build. MSRP: $309.99 // rainierarms.com FINAL THOUGHTS: Once you decide on a lower and build it out, next comes the upper receiver assembly. You can take the same approach and piece together an upper just the way you like it, producing a tailormade rifle that meets your needs. Or, if you want to avoid the assembly process, you can simply purchase an AR-10 complete upper receiver. Either way, there are plenty of options to choose from when building an AR-10. 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