Rosco Mfg Bl-105-Hb-300Blk-7-P Bloodline 300 Out 10.50" Nitride 4150 Cmv Br

The Rosco Manufacturing Bloodline 300 is a 10.5-inch rifle barrel purpose-built for short-barreled rifle (SBR) and pistol-caliber builds where barrel length and performance need to work together. Chambered in .300 Blackout, this barrel pairs a mid-length gas system with a 4150 Chrome Moly Vanadium steel core and a durable nitride finish—giving you a compact upper that handles both supersonic and subsonic ammunition without the fragility of lighter designs. The .750-inch gas block journal accommodates standard components, and the engineering behind the Bloodline series reflects input from both civilian shooters and professional end-users who demand reliability in tight packages.

Rosco Manufacturing builds barrels for specific applications rather than applying one-size-fits-all specs across their lineup. The Bloodline 300 in this 10.5-inch length is engineered with dwell time and gas port sizing dialed in for the shorter sight radius and compact handling of SBR platforms. Whether you're running suppressed, shooting subsonic loads, or building a versatile truck gun, the geometry here supports consistent performance without over-gassing or short-stroking your bolt carrier group.

The nitride finish protects the barrel from corrosion and wear while maintaining a clean, professional appearance. At 10.5 inches, you get effective range for intermediate distances—useful for hunting, defensive work, or precision rimfire-style shooting at moderate yardage. This is a serious barrel for builders who understand the demands of NFA-regulated platforms and want quality that won't let them down.

Key Features

• .300 Blackout chambering—ideal for suppressed shooting and subsonic ammunition
• 10.5-inch barrel length optimized for SBR and pistol builds
• 4150 Chrome Moly Vanadium steel with nitride finish for durability and corrosion resistance
• .750-inch gas block journal for standard AR components
• Mid-length gas system tuned for dwell time and reliability in compact configurations
• Purpose-engineered for suppressed and unsuppressed use

Specifications

Frequently Asked Questions

Is this barrel legal for civilian use?

All NFA (National Firearms Act) rules apply. A 10.5-inch .300 Blackout barrel mounted on an AR-15 platform without a stock may require NFA registration depending on your build configuration and local laws. Consult your local and federal regulations before assembly.

What is this barrel designed for?

The Bloodline 300 is engineered specifically for short-barreled rifle (SBR) and pistol builds in .300 Blackout. It works well with both suppressed and unsuppressed shooting, and handles subsonic loads effectively. The mid-length gas system is tuned for the compact platform to avoid over-gassing or reliability issues.

What's the .750-inch gas block journal?

The gas block journal is the cylindrical surface where your gas block attaches. A .750-inch diameter is standard on most modern AR barrels and accommodates commonly available .750 gas blocks used in short-barreled builds.

Can I use this barrel for hunting?

Yes. The 10.5-inch Bloodline 300 is effective for hunting at moderate ranges. .300 Blackout is capable and commonly used for deer and similar game, though effective range is shorter than longer barrel configurations. Performance will vary with ammunition choice and shot placement.