How to Assemble AR15 Upper (Complete Guide w/ Pictures!) - 80 Percent Arms

While the 5.56mm NATO cartridge has been the standard for the AR15 platform, enthusiasts are increasingly exploring specialty calibers to diversify their shooting experiences. In 2024, AR15 upper options beyond the traditional 5.56mm offer shooters the opportunity to customize their firearms for specific purposes, from long-range precision to increased stopping power. Let’s delve into some noteworthy specialty calibers and the AR15 upper assemblies that accommodate them.

  1. 6.5mm Grendel: The 6.5mm Grendel has gained popularity for its excellent long-range capabilities and superior ballistics. AR15 uppers chambered in 6.5mm Grendel typically feature longer barrels, optimized for accuracy and velocity. Brands like Alexander Arms offer dedicated uppers that enable shooters to harness the potential of this precision-oriented caliber in their AR15.
  2. 300 Blackout: Renowned for its versatility, the 300 Blackout provides an effective solution for both short-range and suppressed shooting. AR 15 Complete Upper assemblies chambered in 300 Blackout often come with shorter barrels, making them suitable for close-quarters engagements. Manufacturers like Aero Precision and Radical Firearms offer 300 Blackout uppers, allowing users to adapt their AR15s for various scenarios.
  3. 6.8mm SPC (Special Purpose Cartridge): Developed to improve terminal ballistics over the 5.56mm NATO, the 6.8mm SPC offers enhanced stopping power. AR15 upper assemblies chambered in 6.8mm SPC typically come with specialized barrels designed to optimize performance. Brands like LWRC International and Wilson Combat provide reliable options for those seeking increased lethality in their AR15 platform.
  4. 450 Bushmaster: For those desiring significant stopping power, the 450 Bushmaster is a robust option designed for big-game hunting and large-caliber enthusiasts. AR15 uppers in 450 Bushmaster often feature heavy barrels and reinforced construction to handle the increased recoil and power. Bushmaster Firearms and Radical Firearms are notable manufacturers offering 450 Bushmaster uppers for the AR15.
  5. 7.62x39mm: Borrowing from the AK-47’s caliber, the 7.62x39mm offers a larger projectile with more energy. AR15 uppers in this caliber are designed to accommodate the unique magazine dimensions of the 7.62x39mm round. Brands like CMMG and PSA provide options for those looking to experience the punch of this Soviet-designed cartridge on their AR15 platform.

Exploring specialty calibers beyond 5.56mm opens up new possibilities for AR15 enthusiasts. Whether you seek precision, versatility, or increased stopping power, the diverse range of AR15 upper options in specialty calibers allows you to tailor your firearm to meet specific shooting requirements in 2024.