AR10 vs LR308: Know the Difference

Welcome to your guide on AR10 and LR308 rifles. In this comprehensive article, we’ll explore the differences between these behemoths and dive into calibers and building tips for these two popular firearms. Whether you’re a seasoned shooter or a beginner looking to expand your knowledge, this guide will equip you with valuable insights to enhance your shooting experience.

Understanding the Difference Between AR10 and LR308

To fully understand the difference between the AR10 lower and LR308 lower, we need to explore their history and the distinctions between these two rifles today. The AR10 rifle was created by Eugene Stoner for Armalite in the 1950s and paved the way for the popular AR15 and M16 rifles. More recently, the LR308 is a variation of the AR10 made by DPMS Panther Arms. It adds its own features while building upon the AR10's foundation. Despite being developed about 60 years apart, both rifles aim to offer shooters a versatile and customizable semi-automatic rifle that can achieve accurate shots.

The general summary is that in today's everyday speak, when someone says "AR10," whether they know it or not they are most likely referring to the LR308 pattern. It's kind of like Kleenex vs Tissue. A tissue could've been made by any company. But Kleenex is a specific brand of tissues. In our case, there is a huge abundance of companies that make LR308 rifles and parts for the platform. However, Armalite is the company/brand that created the original design.

Receiver Compatibility Considerations for Building an AR10 and LR308

AR10 Lower:

• Standardized pattern for greater parts interchangeability.
• Components like barrels, handguards, and stocks can be easily swapped between different manufacturers following the AR10 lower and upper specs.

LR308 Lower:

• May feature slight design variations.
• May require specific components tailored to the particular LR308 model.

Important Steps for Building an AR10 or Modifying an Existing AR10:

Thorough Research:

• Conduct thorough research on receiver compatibility and component requirements.
• Ensure that the selected parts are compatible with your chosen rifle model.

Safety First:

• Always prioritize safety during the building or modification process.
• Follow proper guidelines and ensure the correct assembly of components.

While these rifles may seem and work alike at first, they have a few design distinctions. The AR10 lower usually is a bigger receiver and is famous for working with the .308 Winchester/7.62x51mm NATO cartridge. The LR308 is based on the AR10 design but can have different specs depending on the maker and design. To put it simply, the connection between the two is like the basic math rule: "A square is a rectangle, but a rectangle is not a square."

Photo Credit: Bear Creek Arsenal

Military Adoption of AR15 and AR10

In today's world, the US military mostly uses AR15-style rifles instead of AR10 rifles for regular infantry purposes. The AR15, which shoots 5.56mm rounds, offers several advantages that meet the military's needs. While the military used to rely on .30 caliber rifles during WW2 and even into the late 70s, the demands of modern times have shown that the smaller 5.56 ammo is the preferred choice.

The AR15's light and compact design brings big benefits to the battlefield. Soldiers can move around more easily and handle different combat situations with less difficulty because the weapon is lighter and smaller. This advantage is especially important in fast-paced environments where speed and agility matter a lot.

Key advantages of the AR15:

Ammo Capacity — Standard mags for the AR15 platform are capable of 30 rounds of 5.56 while the AR10 mag standard is 10. An uptick of 200% in the capacity of lifesaving ammo. This also offers a good tradeoff for soldiers, allowing them to carry more rounds without more weight. But if you’re looking for more in the way of mag capacity, check out these Magpul and Hexmag options for your AR10 lower.

Recoil Management — Recoil from the smaller cartridge enables soldiers to keep accuracy tight and engage targets rapidly. More accuracy and volume of firepower enhance their overall strength in combat situations. Or in other words, tighter groups with more rounds on target. See, high school math and science CAN be fun!

Weight — Shedding weight is crucial for long hauls and the AR15 platform can offer a little reprieve to the tune of an average of two pounds when switching from the AR10. I know it doesn’t sound like much but factor in the 45+ pounds of a ruck and any additional gear, that weight can add up quickly for a soldier on a long hike.

The compact size and versatility of the AR15 make it highly suitable for close-quarters conflicts and urban warfare as most conflicts are now seeing. Its design and accessory compatibility provide adaptability and customization options for soldiers.

Let’s not forget that the US military still uses the larger bore platform in certain situations. The smaller AR15 platform is mainly used in standard infantry use. The AR10 or its variant, the SR-25, is geared toward marksman roles or specialized units. The AR10's larger caliber and longer-range capabilities make it great for scenarios where increased power and accuracy at distance are necessary but can still be used in door-to-door scenarios if the need arises.

Photo Credit: Bear Creek Arsenal

Exploring AR10 Calibers

Now that you’ve been bombarded with technical specs regarding the AR10 lower design and history…what about the caliber choice for your newly minted rifle? Different AR10 calibers offer a wide range of options to suit different shooting needs. Let's explore some of the popular AR10 calibers used for the platform and their pros and cons.

.308 Winchester

The OG big bore caliber, also known as 7.62x51mm NATO, is the most common round tagged for the AR10 and is arguably one of the most trusted on the market. It’s a versatile cartridge widely used for big game hunting, target shooting, and military uses. The .308 offers excellent long-range accuracy and a wide variety of ammo options make it a popular choice among shooters.

.243 Winchester

Almost as old as the granddaddy .308. Just as reliable. The tried and true .243 Winchester was originally developed as a hunting cartridge in 1955 but has found its place in the AR10 platform. It offers a flat trajectory and manageable recoil. And its excellent accuracy makes it suitable for varmint hunting, predator control, and even some medium-sized game.

6.5 Creedmoor

Pull up a seat to the kiddy table ‘Junior’. The 6.5mm Creedmoor is a relatively new caliber that has gained popularity in recent years. Even though it isn’t as old as its’ elders (developed in 2007), it definitely drives home its purpose with amazing long-range ballistics, impressive accuracy, and decent recoil. The 6.5mm Creedmoor has gained a reputation as a superior choice for precision shooting competitions and long-range hunting due to its flat trajectory and excellent terminal performance.

Comparing different AR10 calibers requires consideration of factors such as ballistics, recoil, and accuracy. The .308 Winchester, with a larger bullet diameter and heavier projectiles, offers exceptional performance and is ideal for hunting larger game. In long-range precision shooting, the 6.5mm Creedmoor shines with its high ballistic coefficient and notable downrange performance. For all-around shooting needs, the .243 Winchester with its flat trajectory and mild recoil provides a “middle of the road” option between the other noted calibers.

AR10 caliber selection for hunting or precision shooting can be a daunting task. For hunting, the intended game size, typical engagement distances, and local regulations regarding minimum caliber requirements (such as the prohibition of .223 calibers in certain states for deer hunting) are necessary considerations. The right AR10 caliber choice depends on specific shooting needs and preferences.

Before heading out to the range or backcountry, it’s crucial to perform final checks and function testing on your firearm PRIOR to the actual use. Building an AR10 is a lot like building a classic car, you don’t want parts left over. Ensure all components are properly installed. Check for proper headspace and test the rifle to ensure reliable and safe operation. The last thing you want is to find a catastrophic failure when you’ve backpacked three miles into the wilderness and you’ve ultimately ruined your weekend due to poor workmanship. And lastly, zero your optic. I know it’s like beating a dead horse but it would be bittersweet if you built a beautiful sub-MOA beast and send your shot a foot over your intended target.

Possible AR10 Builds

Options are nearly limitless when you decide to jump into the world of building an AR10. You can customize your rifle to match your shooting goals, whether it's a lightweight and compact carbine or a long-range precision rifle. While we won't cover specific builds in this article, we suggest checking out these blog posts for an overview of various builds, component choices, and expert advice: 

• AR10 Build Guide
• Best AR10 Triggers
• Your next AR15: build it or buy it?

Photo Credit: Ghost Gunner

DPMS vs. Armalite: Understanding the Controversy

The AR10/LR308 platform is based on two prominent variations: the DPMS pattern and the Armalite pattern. DPMS pattern rifles typically feature a high-profile, rounded upper receiver, while Armalite pattern rifles have a distinct angular, low-profile receiver (see the figure above for visual reference). These designs can impact parts compatibility and may influence your decision when building or modifying an AR10/LR308.

DPMS and Armalite pattern rifles deliver reliable performance and compatibility with a wide range of components. However, it's important to note that certain parts, such as handguards and bolt carrier groups, may require specific variations tailored to either DPMS or Armalite pattern rifles. Understanding these factors will help you to make well-informed choices when selecting parts for your build.

DPMS pattern rifles are renowned for their extensive availability of aftermarket parts and accessories, making them easier to customize. However, Armalite pattern rifles are often favored for their sleek, low-profile design and strict loyalty to the original AR10 specifications. Each variant has its merits, and the ultimate choice depends on you and your intended use.

Practical Considerations, and FAQs

Both hunting or quick movements with an AR10 or LR308 can lead to the struggle bus and weight ultimately becomes an enemy. Generally, AR10 rifles tend to be heavier because of their larger receiver size and the use of the .308 Winchester cartridge. LR308 rifles, though still substantial, may offer a slightly lighter alternative. Determine the ideal weight balance between firepower and portability based on your specific needs.

Even though the AR-10 and AR-15 platforms share similarities, they serve different purposes and excel in specific use cases. The AR-10, with its larger caliber options and increased power, is ideal for long-range shooting and hunting larger game, whereas the AR-15, chambered in smaller calibers like 5.56mm NATO, is popular for its versatility, lighter weight, and perfect for close to medium-range engagements.

The .308 Winchester and AR10 are often mentioned together due to their historical connection and caliber compatibility. The .308 Winchester is a versatile cartridge widely used in various rifles, including the AR-10. It's important to note that the AR-10 is not limited exclusively to the .308 Winchester and can also be chambered in other calibers.

Should you buy the AR10 or the LR308 Lower?

The AR10 and LR308 offer shooters a wide array of options in terms of differences. Different calibers and building opportunities are vast and sometimes confusing. Understanding the historical background, design distinctions, and receiver compatibility is crucial when jumping on an AR10/LR308 build or modification. Considering performance factors and addressing practical uses for your lower platform will help you make informed decisions based on your shooting needs. 

As an AR10 enthusiast, you’re part of a unique community of shooters who appreciate the power and versatility of these rifles. Whether you’re drawn to the beast .308 Winchester or the impressively newer 6.5mm Creedmoor, start with our  AR10 80 lower and we'll help you find the rest of the parts you need to complete your build!