Upgrade your AR-15 with our premium selection of 300 Blackout uppers, engineered for maximum reliability and peak suppressor performance. Whether you are building a compact 8" or 10.5" home defense pistol or a versatile 16" hunting rifle, we offer complete and stripped uppers built to cycle both subsonic and supersonic ammo flawlessly. Shop uppers featuring fast 1:8 and 1:7 twist rates, optimized pistol-length gas systems, and extended .30 caliber feed ramps to ensure your build runs smoothly right out of the box.
READY TO SHIP
READY TO SHIP
Supersonic Versatility. Subsonic Capability.
A Ballistic Barn 300 Blackout upper gives AR-15 owners the flexibility to use lightweight supersonic ammunition for hunting and general-purpose shooting or heavy subsonic ammunition for reduced-velocity suppressed applications. The cartridge performs efficiently from shorter barrels while retaining compatibility with standard AR-15 bolt carrier groups and magazines.
The 300 Blackout was designed to deliver useful .30-caliber performance from the AR-15 platform without requiring a proprietary bolt carrier group. Its ability to operate with both supersonic and subsonic ammunition makes it especially popular for compact rifles, hunting builds and suppressor-ready configurations. Learn more about the cartridge in our 300 Blackout cartridge guide.
The 300 Blackout uses a standard AR-15 bolt carrier group and can fit in common AR-15 magazines, but the ammunition must never be loaded into or fired through a .223 Remington or 5.56 NATO barrel. Clearly label magazines, keep ammunition separated and verify the chamber marking before loading.
Ballistic Barn 300 Blackout uppers are assembled in-house using carefully selected components. Every assembled upper is inspected for fit and function and individually checked for proper headspace using Manson GO and NO-GO gauges before shipping.
| Feature | Specification | Why It Matters |
|---|---|---|
| Caliber | 300 AAC Blackout | Provides .30-caliber capability with both supersonic and subsonic ammunition in the AR-15 platform. |
| Platform | AR-15 | Fits compatible standard-dimension AR-15 lower receivers. |
| Common Barrel Twist | 1:7 or 1:8 | Supports a broad range of projectile weights, including heavy subsonic bullets. Browse our AR-15 barrels for available barrel options. |
| BCG Compatibility | Standard .223 / 5.56 NATO | No proprietary bolt face or caliber-specific carrier is required. See our AR-15 bolt carrier groups for compatible component options. |
| Gas System | Pistol length commonly used | Short gas systems are commonly paired with 300 Blackout barrels to support reliable operation across varied loads. |
| Muzzle Thread | Typically 5/8x24 | Common threading for .30-caliber muzzle brakes, flash hiders and suppressor mounts; verify the individual barrel listing. |
| Magazine Compatibility | Standard or dedicated 300 Blackout AR-15 magazines | Standard magazines often work, while dedicated magazines may improve feeding with certain heavy projectiles. Browse our magazine selection for available options. |
| Ammunition Types | Supersonic and subsonic | Allows the same upper to be configured for hunting, general-purpose use or suppressed shooting. |
Every Ballistic Barn 300 Blackout upper is assembled, inspected for fit and function, and checked for proper headspace using Manson GO and NO-GO gauges before shipping. Configurations that include both a compatible bolt carrier group and charging handle are sold as complete uppers. Review the individual product listing to confirm the included components and available options.
Yes. A 300 Blackout upper is designed for the AR-15 platform and fits compatible standard-dimension AR-15 lower receivers. The correct buffer setup, magazine and ammunition should still be confirmed for the selected configuration.
The 300 Blackout uses a standard AR-15 bolt carrier group designed for .223 Remington and 5.56 NATO. No caliber-specific bolt face is required.
Many 300 Blackout loads work in standard AR-15 magazines designed for .223 Remington and 5.56 NATO. Dedicated 300 Blackout magazines may improve feeding with certain heavy or subsonic projectiles. Magazines should be clearly marked to prevent ammunition mix-ups.
Practical range depends heavily on whether supersonic or subsonic ammunition is used. Supersonic loads are commonly selected for hunting and general-purpose use at short to moderate distances, while subsonic loads are intended primarily for reduced-velocity suppressed applications.
Yes. With appropriate supersonic hunting ammunition, the 300 Blackout is commonly used for deer, hogs and similar game where lawful. Ammunition selection, shot placement, expected distance and local hunting regulations should always be considered.
The 300 Blackout performs efficiently from relatively short barrels. Many shooters choose 8- to 10.5-inch barrels for compact or suppressed configurations, while 16-inch barrels are common for rifles that do not require short-barrel registration. The best choice depends on ammunition, intended use and applicable law.
A 1:7 or 1:8 twist is common. Faster twist rates are often selected to stabilize heavier subsonic projectiles, while both can work well with many supersonic loads. Always match the barrel twist to the ammunition you plan to use.
Yes. The 300 Blackout was designed to work with both subsonic and supersonic ammunition and is widely used in suppressed AR-15 configurations. Reliable operation depends on barrel length, gas-system setup, ammunition, suppressor and buffer components.
No. A 300 Blackout cartridge can create a dangerous obstruction if chambered in a .223 Remington or 5.56 NATO barrel. Always verify the barrel marking, keep ammunition separated and clearly label magazines.
Every upper is assembled in-house using carefully selected components, individually inspected, and checked for proper headspace using Manson GO and NO-GO gauges. Available configurations allow customers to select components that better match their intended ammunition and application.