Modern sporting rifles, particularly the AR-15 and AR-10 platforms, have become increasingly popular among civilian shooters, hunters and competitive marksmen. The .223 Remington and its military counterpart, the 5.56x45mm NATO, are the most common chamberings for AR-15 rifles. These cartridges offer low recoil, flat trajectories and good accuracy at moderate ranges. However, the growth of additional chamberings in MSRs continues to gain momentum. We’ll explore several of the top chamberings for AR-15 and AR-10 rifles, including their unique characteristics and ideal uses.
AR-15 Chamberings
.300 AAC Blackout
Developed to provide .30-caliber performance in the AR-15 platform, the .300 Blackout has gained popularity for its versatility. It offers similar ballistics to the 7.62x39mm cartridge but can be used with existing AR-15 magazines and bolts. The .300 Blackout excels in AR pistols and short-barreled rifles and is particularly effective when used with suppressors. It’s an excellent choice for home defense and hunting medium-sized game at more moderate ranges. The ability to use both supersonic and subsonic loads adds to its flexibility.
6.5 Grendel
The 6.5 Grendel was designed to enhance the long-range capabilities of the AR-15 platform. It offers excellent accuracy and retained energy at extended ranges, making it a popular choice for long-range target shooting and hunting medium-sized game. The 6.5 Grendel provides a flatter trajectory and better wind resistance compared to the .223 Rem., while still maintaining manageable recoil. This cartridge is particularly favored by those who want to stretch the capabilities of their AR-15 without moving to a larger rifle.
6mm ARC (Advanced Rifle Cartridge)
One of the newer entries in the AR-15 chambering lineup, the 6mm ARC, was developed to offer enhanced long-range performance and terminal ballistics. It provides an excellent balance of velocity, energy and recoil, making it suitable for a wide range of applications including long-range target shooting, hunting predators and medium-sized game as well as tactical use. The 6mm ARC offers better ballistics than the 6.5 Grendel while fitting in the same magazine capacity, making it an attractive option for those seeking maximum long-range performance from the AR-15 platform.
.22 ARC (Advanced Rifle Cartridge)
The .22 ARC (Advanced Rifle Cartridge) is a relative newcomer to the AR-15 platform, designed to offer improved performance over the .223 Rem. while maintaining compatibility with standard AR-15 components. It pushes a .224-inch bullet at higher velocities than the .223 Rem., resulting in flatter trajectories and increased energy at longer ranges. The .22 ARC is particularly well-suited for varmint hunting and long-range target shooting, offering reduced wind drift and improved terminal ballistics compared to the .223 Rem. While it’s still gaining traction in the market, the .22 ARC represents an interesting option for shooters looking to enhance their AR-15’s capabilities to .22-250 performance levels without significant modifications.
AR-10 Chamberings
.308 Winchester / 7.62x51mm NATO
The .308 Winchester and its military equivalent, the 7.62x51mm NATO, are the most common chamberings for AR-10-style rifles. This cartridge offers more power than traditional AR-15 chamberings, making it suitable for long-range target shooting, big game hunting, and tactical applications. The .308 provides excellent accuracy and energy retention at extended ranges, though at the cost of increased recoil and reduced magazine capacity compared to smaller cartridges. Its widespread availability and proven performance make it a popular choice for AR-10 users.
6.5 Creedmoor
In recent years, the 6.5 Creedmoor has surged in popularity for both bolt-action and semi-automatic rifles, including the AR-10 platform. It offers superior long-range ballistics compared to the .308 Win., with a flatter trajectory and better wind resistance. The 6.5 Creedmoor excels in long-range target shooting and has become increasingly popular for hunting applications. It provides an excellent balance of accuracy, range and moderate recoil, making it a versatile choice for the AR-10 platform.
.243 Winchester
For those looking for a lighter-recoiling option in the AR-10 platform, the .243 Winchester is an excellent choice. It offers a flat trajectory and good accuracy, making it suitable for long-range target shooting and hunting varmints to medium-sized game. The reduced recoil of the .243 Win. can be beneficial for smaller-statured shooters or those who are recoil-sensitive. While it may not have the same long-range capabilities as some larger calibers, it provides a good balance of performance and shootability.
.338 Federal
For those seeking maximum power from the AR-10 platform, the .338 Federal offers an interesting option. Based on the .308 Win. case necked up to .338 caliber, this cartridge provides excellent energy and terminal performance for hunting large game. It offers better penetration and energy transfer than the .308 Win., making it suitable for taking larger animals at moderate ranges. However, the increased recoil and reduced magazine capacity may make it less ideal for target shooting or tactical applications.
Making Your Choice
The wide variety of chamberings available for modern sporting rifles allows shooters to tailor their firearms to their specific needs and preferences. Whether you’re looking for a versatile all-around performer, a long-range precision tool or a hard-hitting hunting rifle, there’s likely a chambering (or two) that fits your requirements. New cartridges like the 6mm ARC and .22 ARC are pushing the boundaries of what’s possible with the smaller AR-15 platform. In the AR-10 world, the .308 Winchester/7.62 NATO is a popular all-around choice, while the 6.5 Creedmoor has gained significant traction for its superior long-range performance.
Ultimately, the best chambering for your modern sporting rifle will depend on your intended use, shooting environment and personal preferences. Consider factors such as desired effective range, recoil tolerance, rifle weight, ammunition availability and terminal performance when making your selection. Also, consider the right optic for your chambering and intended use. With the right chambering and optic, your MSR can be an incredibly versatile and effective tool for your intended shooting applications.
