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AR 308 Frequent Asked Questions

The AR 308 and AR10 are both large-frame AR-style rifles chambered in full-power rifle cartridges like .308 and 6.5 Creedmoor.

Much like the AR-15, the AR 308 rifle platform is extremely modular, modern, and has a plethora of aftermarket components that allow you to endlessly customize it to your hearts content. Think of it as a scaled-up version of the AR-15 that shoots the larger caliber bullets and other cartridges that are too large to fit in the smaller platform. AR308s can be exceedingly accurate, and many professionals choose this platform for their designated marksman or sniper teams.

The larger AR308 platform offers many advantages over the AR15, as well as some disadvantages. However, you should not think of them as competitors. As a matter of fact, we think you should get both, as they each fill different roles in a collection. Whether you’re a hunter, competitor, or defensive marksman, an AR 308 gives you the advantage of accuracy and distance with a reliable, modular weapon system. No other full-power semi-automatic has the same parts or product support as the AR 308 platform, making it one of the most customizable rifles in America.

The AR10 or ArmaLite 10 is widely used terminology for someone looking for an AR style rifle chambered in .308. Although, most of the time, using this term is not technically accurate. The AR-10 was designed by Eugene Stoner in the late 1950’s but went through multiple changes to scale it down for use with the .223 Remington and thus the AR-15 was born. When ArmaLite when under, they sold the rights of both the AR-15 and AR-10 to Colt who then continued manufacturing AR-15 pattern rifles while the AR-10 fell by the wayside.

And then it gets slightly more confusing, as the trademark for AR-10 was sold to ArmaLite Inc.—a newly formed company—who then developed the AR-10B which uses its own proprietary receiver and bolt carrier group dimensions. This version of the AR-10 is what the SR-25 rifle used by the United States Military is based on as well as the Lewis Machine and Tool 308MWS.

So where does AR 308 come into play in all this? With the AR-10 name being taken and ArmaLite Inc. and the design being less modular, DPMS Panther decided to bring their own version to the market that more closely resembles the AR-15 in terms of outward appearance and modularity. In 2004 they released the LR-308. This version became extremely popular on the civilian market which eventually led to many companies producing their own versions with the same dimensions and aftermarket companies producing parts that were compatible with them all. And now, AR-308 is the accepted terminology to identify if something is DPMS or LR-308 pattern.

Fast forward a few more years and DPMS released the GII and POF released the Revolution which brings the LR 308 even closer to the AR-15 size. However, these are still proprietary in their main dimensions meaning only small parts will be interchangeable.

Now that you know a brief history behind the terminology, we can look at the parts themselves, so you can make an informed decision on which parts you can upgrade on your new 308 AR rifle.

Luckily, chances are, if you have already bought a 308 AR pattern rifle in the last 15 years, it is most likely a DPMS pattern which means it will be easy for you to find parts. However, it is still important to know the differences. One quick way to determine if a rifle is ArmaLite or DPMS pattern, is to look at the rear where the upper and lower receivers meet. An ArmaLite AR-10 rifle will have a diagonal cut where the receivers meet, and a DPMS AR-308 rifle will have a rounded cut.

An important thing to consider is that the bolt carrier groups are also not interchangeable and will not headspace correctly if they are not mated to the barrel extension they were designed for. The parts are close enough dimensionally that it looks like they might work, but this is a dangerous lie. Make sure you are buying the correct parts. If it doesn't say it is the part you need, verify with the retailer or the manufacturer if the retailer can't or won't tell you.

Another important thing to note when upgrading parts on your AR .308 rifle is handguard dimensions and how they relate to the receiver. The DPMS LR-308 pattern rifles have two types of upper receivers they can come with. Low profile and high profile. This refers to the height of the tang or where the flat top picatinny rail will meet the picatinny rail on your handguard. The low-profile upper receiver has a tang height of 1/8th of an inch while the high profile is thicker with a 3/16th inch height. The most common you will see is high profile versions and all of our AR 308 handguards are labelled to make it easy when you upgrade.

Here is a complete list of parts that are generally not interchangeable between the AR-308 and AR-10 platforms:


· Upper and Lower Receiver


· Buffer Assembly (tube, buffer, spring)


· Gas tube (The AR10’s is too long)


· BCG (Head spacing differences)


· Handguard


· Barrel nut


· Magazine catch


However, some non-essential parts can be swapped between the AR-308 and AR-10 such as:


· Dust Cover


· Charging Handle


· Gas Block


· Trigger Assembly


· Takedown springs and detents


· Pistol Grip


· Trigger Guard


· Castle Nut


· Safety Selector Lever


Because the large platform AR market is not as set in stone in terms of parts tolerances as the AR-15 market, we generally recommend buying a complete AR 308 rifle and upgrading parts as you go instead of building one from the ground up. If you buy a DPMS pattern rifle, stick to DPMS pattern parts and the same for ArmaLite and you will be a happy camper. Additionally, sticking to the same brand will help prevent a lot of headaches when you get to the range.

One of our favorite brands that is commonly available and utilizes the DPMS platform is Aero Precision. Piecing together an M5 upper and lower from Aero Precision is just as reliable as buying a rifle whole. If you stick with them, you can easily get an AR308 rifle that will be reliable.

When shopping for a new AR 308, you will find that the most popular 2 chamberings are .308 Winchester and 6.5 Creedmoor. Each has its benefits and weak points, but you can’t go wrong with either.

.308 Winchester is an American classic, making it one of the most accessible rifle cartridges on the market. It’s a capable round from point-blank to 1000 yards, and its history with the U.S. Military makes it one of the most well-researched rounds on the market. With .308 Winchester, you’ll have exceptional parts and ammunition support for the lifetime of the rifle.

If you want a more specialize long-range marksman round, 6.5 Creedmoor is your pick. Recently adopted by SOCOM, 6.5 Creedmoor is a 6.5mm projectile with an impressive ballistic profile, making it easy to hit targets to 1000 yards and beyond. At distance, this round will outperform .308 Winchester across the board, but it comes at the cost of ammo cost and reduced barrel life.

For all-around performance and value, .308 Winchester is hard to beat. That said, if you want a true marksman’s rifle, 6.5 Creedmoor is the latest and greatest in ballistics science.

So which rifle should you get? If you choose to go with the AR 308 rifle, then you might want to check out the SIG Sauer 716i Tread that features a 16 inch barrel and a free float M-LOK handguard for endless accessory placement options. The flat top upper allows you to easily attach the scope of your choice and the enhanced single stage trigger is perfect for tight groups and taking any game in North America. The adjustable gas block is easy to use, so you can tune your rifle to your preferred round.

If you are looking to get into the 308 AR rifle game for a little less, we have great options from Del-Ton that utilize Magpul two piece handguards and A2 style front sight post gas blocks that are still solid contenders. And remember, you can always upgrade. Another great reason why you might want an AR 308 complete rifle is that the caliber is better suited for shorter barrels.

With less options to choose from in the AR10 rifle platform, you are lucky that we carry one of the best. Lewis Machine and Tool .308 AR 10 rifles are based on the ArmaLite platform but even they only recommend using their uppers with their lowers. And that is not a problem because there should not be anything that you want to change on these rifles. They have fully ambidextrous lower receivers and upper receivers with truly monolithic handguards for rock solid set up and a quick change barrel system so you can easily go from 7.62x51 to 6.5 Creedmoor.

The Daniel Defense DD5v4 Rifle also closely resembles the ArmaLite AR-10 platform, but the receivers are not compatible with any other brands. This one, however, is chambered in 6.5 Creedmoor with an 18 inch barrel and a free float handguard. The DD5v4 6.5 Creedmoor AR10 rifle is a great option for someone that wants a semi-automatic platform that is great for hunting and long range precision shooting. Like the LMT offerings, it also features a fully ambidextrous lower receiver.

If you have any questions, don't hesitate to send us a message at info@primaryarms.com or call us at 713-344-9600.