A Guide to AR-10s and LR-308s

30th Sep 2021

A Guide to AR-10s and LR-308s

The AR-10 and LR-308 are premier rifles with many visual similarities that both feature unique properties and functional mechanisms. Historically, each gun gets its origin from World War II. At the time, the M1 Garand was one of the most popular rifles. Shortly following the war, the United States military realized it needed to replace the M1 wither a newer and more effective service rifle.

The military was looking for a high-quality rifle capable of fully automatic fire while being lightweight and accurate, among other improvements. As a result, the AR-10 was made, which led to the later iteration of the AR-15. Several decades after the AR-10 was designed, the LR-308 would be created, which shares many visual similarities with the AR-10.

History of the AR-10 and LR-308

The AR-10 was developed by Eugene Stoner, who moved away from the traditional wood stock of the M1 Garand and adopted a straight-line design during its creation. The ArmaLite AR-10 features iron sights, a patented gas system and a recoil compensator. Within the gas system, gas from a fired cartridge forms into a gas block in the front sight assembly through a gas port located in the barrel.

Stoner's initial AR-10 designed was completed in 1955 for the 7.62x51 millimeter NATO cartridge, which is similar to the commercial .308 Winchester. The AR-10 is commonly known as the ArmaLite 10 and is a stronger and more powerful predecessor to the AR-15. While many people may refer to the AR-style .308 chambered rifle as an ArmaLite AR-10, that's not always accurate. Furthermore, the DPMS's version of this rifle is known as the LR-308.

While the AR-10 has a long history, here's a quick timeline of the gun's history:

  • After World War II, the M1 Garand became obsolete.
  • The U.S. Army needed a new rifle that was lightweight and more accurate.
  • The AR-10 competed against the FAL and M14.
  • Stoner's AR-10 was lightweight and superior to the T48 and 744E4.
  • George Sullivan, president of ArmaLite, wanted to modify the AR-10 with an aluminum barrel.
  • The flawed aluminum barrel burst when the Army tests this revised model.
  • After this failed test, the Army denied the AR-10 and said it required fine-tuning.
  • ArmaLite changed directions with the AR-10 and licensed it to Artillerie-Inrichtingen, a Dutch manufacturer.
  • ArmaLite struggled to stay in business until the United States began the U.S. Continental Army Command Rifle Program.
  • Eugene Stoner, Bob Fremont and Jim Sullivan worked together to create a rifle that met the needs of the U.S. Army.
  • The AR-10 led to the creation of the AR-15, which became one of America's most popular rifles.

Basics of the AR-10

One of the most notable aspects of an AR-10 is its lightweight design, especially compared to .308 semi-auto rifles. The lightweight design is due to its direct impingement, different from the piston-driven design found with most other .308 semi-auto rifles. While an AR-10's weight varies from model to model, the average AR-10 weighs approximately 7.25 to 8.9 pounds, not including the magazine.

The AR-10 can take a detachable magazine and offers adjustable rear sight for windage, in-line stock and pistol grip. The Picatinny rail on the AR-10's platform serves as the ideal mounting solution for red dot, scope or holographic sights. ArmaLite faced various financial issues, causing them to sell the AR-10's designs to Colt, which would then provide the rifle to the U.S. Army.

What's the Difference Between the AR-10 and LR-308?

The AR-10 and LR-308 are rifles that share numerous similarities in terms of appearance. In many cases, someone  may even mistake an LR-308 for an AR-10 if they don't look closely. But despite their visual similarities, the AR-10 and LR-308 function very differently.

Often, the critical aspects of these rifles aren't interchangeable, including the upper and lower receiver, buffer assembly, gas tube and magazine catch. Additionally, the handguard, barrel nut and the bolt carrier group aren't interchangeable. Learning the differences between these two rifles can help you properly identify each.

AR-10 Guide

The AR-10 was invented approximately 30 years before the LR-308 was designed. The AR-10 has an angular cut on the lower and upper receiver. On the other hand, the LR-308's cut is rounded. While Stoner originally patented this design in 1958, it doesn't necessarily provide a functional purpose.

When the original patent expired, numerous companies decided to design a universal mil-spec configuration to place on the market. This configuration is why the AR-10 and the LR-308 appear visually similar. All that being said, the AR-10 is the modern rifle that led to the rifle market being revolutionized.

DPMS LR-308 Guide

Some people often incorrectly identify an LR-308 as an AR-10 due to their visual similarities. While there are many components of the LR-308 that aren't interchangeable, most gun owners can easily find compatible components for the LR-308, adding a layer of convenience.

The LR-308 model also allows for the ability to interchange magazine types, styles and brands. Another benefit of an LR-308 is it's a high-performance rifle that is generally less expensive than other rifle models. The companies that manufacture the LR-308 are highly reputable and are committed to creating premium rifles.

What Parts Are Interchangeable Between AR-10 and LR-308?

Although the AR-10 and LR-308 share visual similarities, they feature many unique internal mechanisms. It's essential to understand which parts of an AR-10 and LR-308 are interchangeable so you can understand which gun will work best for you. Learn more about what parts of the LR-308 and AR-10 are interchangeable:

Parts that Are Not Interchangeable

Lower Receivers

Because the upper receivers of both the AR-10 and LR-308 are different, the lower receiver is designed to accept their corresponding upper receivers. While the LR-308 and AR-10 rifles' bolt carrier groups are visually similar and function the same, there are slight differences in the size and barrel extensions. This size difference means you're unable to mix and match between these two platforms.

Pairing different components can lead to complications. For example, the excess headspace can lead to the case head separating on a cartridge when it's fired. The AR-10 and LR-308 share the safety selector lever, safety spring and detent, magazine release button, and the bolt catch spring and plunger within the lower receiver.

While the bolt catch is shared between both rifles, the roll pin isn't compatible. Additional shared parts include the trigger and spring, hammer and spring, pivot spring and detent, trigger guards and pin and the buffer tube. The AR-10 and LR-308 also share the castle nut, buttstock, receiver end plate, buffer retainer, takedown spring and detent, the disconnector and spring and the pistol grip, screw and washer.

Upper Receivers

DPMS-patterned upper receivers are incompatible with AR-10's platform because there's a difference in shape and size. The LR-308 receiver features a rounded rear facing. On the other hand, the AR-10 upper receivers feature a slant-cut. Therefore, you can't use a DPMS lower with an AR-10 upper or vice versa.

It's also important to note that barrel nuts, handguards and rails are incompatible. However, the LR-308 and AR-10 share the gas block, barrel without the extension and the charging handle. Additionally, the gas tube roll pin, forward assist assembly and the ejection port dust cover are the same between either rifle design.

Bolt Carrier Groups

In terms of the ArmaLite and DPMS bolt carrier groups, the dimensions are very similar — within a few thousandths of an inch from one another. The bolt carrier groups are interchangeable, but it's important to note you can't interchange the bolts between different brands of the bolt carrier. With an ArmaLite bolt carrier, you'll only want to use an ArmaLite bolt. The same goes for a DPMS bolt.

Barrels

The most common barrel extension is the DPMS pattern barrel extension, translating into many 308 AR barrel options. The AR-10 and DPMS LR-308's barrel extensions aren't dimensionally identical, meaning each rifle must use barrels specifically designed for the AR-10 or the LR-308.

An often misleading variable is that many vendors and manufacturers may incorrectly refer to anything .308 as an AR-10. Fortunately, in their specifications and fine print, they'll specify the actual platform compatibility.

Barrel Nuts and Upper Receiver Threads

The barrel nut threads are the internal threads within the upper receiver. The external threads are a function of specific handguard mounting that doesn't relate to barrel installation. The upper receiver threads and barrel nuts are similar to the pattern differences of the DPMS LR-308 and AR-10, but the manufacturers use two different threads. The AR-10's barrel nut threads measure 1 7/16 inches and 18 TPI-3A. On the other hand, the barrel nut threads of the DPMS pattern are 1 7/16 inches and 16 TPI- 2A.

Buffer, Buffer Tube and Buffer Spring

The recoil system of a rifle consists of three parts, including the buffer, buffer tube and buffer spring. The ArmaLite AR-10's buffer dimensions are 5.2 inches, and the rifle buffer tube dimensions are 9 11/16 inches. Finally, the AR-10 rifle buffer spring dimensions are 14 1/8 inches. The DPMS uses an AR-15 receiver extension featuring a .308-specific buffer spring and a short .308-specific buffer.

Gas Tubes

Another important difference between the LR-308 and AR-10 is the length of the rifle's gas system. The ArmaLite AR-10 features a gas tube that measures approximately .325 inches longer than the LR-308. While the LR-308 uses the same gas tube as the AR-15, the AR-10's gas tube is incompatible, as it's longer than both the AR-15 and LR-308's gas tubes.

Magazines

An ArmaLite rifle requires specific magazines for the AR-10. On the other hand, the DPMS LR-308 uses the SR25 magazine pattern, allowing the use of PMAGs. ArmaLite offers two styles of lower receivers, including AR-10A and AR-10B.

ArmaLite also uses two different types of magazines. The original waffle magazines are used for the AR-10A, but these magazines have become outdated. An AR-10A is more commonly paired with Magpul LR 308 PMAGs, which are considered DPMS/KAC SR-25 compatible magazines. It's important to know these magazines as the original AR-10 and 308 AR magazines.

The magazines for the AR-10B are specific to ArmaLite and are based on the M14 magazines, which are the ArmaLite standard. AR .308 rifles don't have mil-spec designated magazines, but they have one magazine style that has become the most common. The DPMS 308 magazine is one of the most universally accepted magazines for the LR-308.

Parts that Are Interchangeable 

  • Dust Cover
  • Charging Handle
  • Gas Block
  • Trigger Assembly
  • Takedown springs
  • Pistol Grip
  • Trigger Guard

Which One Should You Pick?

Both the AR-10 and LR-308 are high-quality rifles that offer unique advantages and are ideal for various applications. There are numerous types of rifles and rifle calibers, each with unique components, aspects and functionalities. Finding the rifle that's right for you is an important step in gun ownership. Some factors you'll want to consider are the overall weight of the rifle and its firing capacities.

Fortunately, the AR-10 and LR-308 are both strong contenders that offer many unique benefits. First, you'll want to consider why you're purchasing a rifle. Determining the applications you need can help you understand what capabilities you're looking for in a rifle.

If you're deciding between an AR-10 and an LR-308, you may want to consider these aspects and benefits:

Benefits of the AR-10

One of the main benefits of the AR-10 is its convenient, lightweight design. The AR-10 offers a dependable and reliable shooting experience for the rifle owner while also being easy to handle. The direct impingement design is what helps the AR-10 be so lightweight, especially when compared to other semi-auto rifles. Another benefit of the AR-10 is that it's a very practical and versatile rifle.

From big game hunting to tactical and defensive applications, the AR-10 is a useful rifle for various situations. The AR-10 is also a magazine-fed semi-automatic rifle, allowing you to reload quickly and easily while firing heavier caliber bullets. It's crucial to note that while the AR-10 is a versatile rifle, it's not ideal for use in close quarters.

Benefits of the LR-308

The LR-308 is a premium rifle that's fairly inexpensive and high-quality. LR-308 owners can customize their rifles and enjoy a high level of accuracy and smooth action. The LR-308 also has fast and precise follow-up shots. While the LR-308 has many benefits, there are certain limiting factors to consider to determine if this rifle is right for you.

The LR-308 is a relatively heavier rifle weighing around 15 pounds, almost double the AR-10. An LR-308 rifle may also be less balanced before barrel cut down and has a heavier stock than other rifles. DPMS has made numerous variations of the rifle, meaning some aftermarket components will only fit certain rifle versions.

Upgrade Your AR-10 or LR-308 With Wing Tactical

At Wing Tactical, we pride ourselves on offering the finest quality rifle components currently available on the market. All of our items are manufactured by reputable companies dedicated to providing top-grade work. Each component is uniquely designed and crafted under the guidance of industry experts.

The Wing Tactical catalog features many AR-15 parts, including upper receiver parts, lower receiver parts, gas systems and more. Explore our accessories, new products and brands to find the perfect component for your AR-10 or LR-308. Upgrade your rifle today and shop our selection of AR-10 and LR-308 parts.

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