Diamondback DB Barrel — 300 Blackout, 8.50" Pistol-Length, Black Nitride, 4150 Chrome Moly Vanadium Steel | Model 300P85H50B8R (UPC: 815875019183)
Optimize your compact AR build with the Diamondback DB 300 Blackout 8.50" Barrel—purpose-built for reliability, durability, and easy maintenance in short, maneuverable setups. Machined from 4150 Chrome Moly Vanadium (CMV) steel and finished inside and out with black nitride (QPQ), this barrel delivers a hardened surface that resists wear, fights corrosion, and cleans up fast. The pistol-length gas system is the sweet spot for 300 BLK in short configurations, supporting dependable cycling across popular supersonic and subsonic loads when paired with the right gas and buffer tuning.
Why Choose This Diamondback 8.50" 300 BLK Barrel?
Short, balanced length (8.50") for compact AR pistols/SBRs that still need dependable velocity and smooth handling.
Duty-grade 4150 CMV steel for heat tolerance and long service life under high round counts.
Black Nitride (QPQ) treatment boosts surface hardness, reduces fouling, and enhances corrosion resistance for easier maintenance.
Pistol-length gas system tuned for 300 BLK’s pressure curve—ideal for both subsonic and supersonic loads with appropriate setup.
AR-15 pattern compatibility for straightforward builds using standard 5.56-based components (bolt, upper, etc.) matched to 300 BLK.
Key Features at a Glance
Caliber: 300 AAC Blackout (300 BLK)
Barrel Length: 8.50 inches
Material: 4150 Chrome Moly Vanadium (CMV) steel
Finish/Treatment: Black Nitride (QPQ), inside & out
Gas System: Pistol-length
Platform: AR-15 pattern pistols/SBRs (where lawful)
Model: 300P85H50B8R
UPC: 815875019183
Color: Matte black
Builder’s note: Confirm twist rate, muzzle thread pitch, gas journal diameter (commonly .750"), and contour/weight for your specific production run to match gas blocks, suppressor mounts/muzzle devices, and preferred bullet weights.
Performance Benefits You’ll Notice
Reliable cycling with 300 BLK: Pistol gas is the proven choice for short 300 BLK barrels, especially when you want flexibility between subs and supers.
Faster, cleaner maintenance: QPQ nitride reduces copper/carbon adhesion, so high round-count range days don’t mean long bench sessions.
Heat and erosion resistance: 4150 CMV plus nitride helps mitigate throat wear, supporting consistent velocities and accuracy potential over time.
Compact handling: 8.50" keeps weight forward minimal for quick transitions in tight spaces and smoother manipulation around barricades and vehicles.
Ideal Use Cases
Suppressed 300 BLK builds (with appropriate adjustable gas and buffer tuning, where lawful)
Home/ranch utility and training platforms that value compact size and controllable recoil
Travel/vehicle stow builds (where lawful) needing minimal overall length
General-purpose range guns that run both bulk supers and precision subsonic loads
Build & Compatibility Checklist
Upper Receiver: Mil-pattern AR-15 compatible with 300 BLK
Bolt Carrier Group: Standard 5.56/.223 BCG (300 BLK uses the same bolt lugs/face); ensure proper headspace
Magazines: Use quality 5.56-style AR magazines dedicated and clearly marked for 300 BLK to avoid ammo mix-ups
Gas Block & Tube: Pistol-length gas tube; verify gas journal diameter for gas block selection
Handguard: Short free-float rail that provides clearance for your muzzle device/suppressor mount
Muzzle Device: Match thread pitch; consider brake/flash hider or suppressor interface tuned for 300 BLK
Buffer System: Heavier buffers and an adjustable gas block are recommended, especially for suppressed/subsonic use
Installation Tips
Inspect & prep: Degrease barrel extension and gas journal; lightly oil mating surfaces.
Torque & align: Install the barrel nut to spec; verify straight gas tube alignment.
Secure the gas block: Align to the port; dimple/pin as desired and use appropriate thread locker on set screws.
Headspace check: Always confirm with GO/NO-GO gauges before live fire.
Function test & tune: Validate last-round bolt hold-open and ejection pattern. For subsonic/suppressed setups, fine-tune with an adjustable gas block and buffer weight.
Specifications
Caliber: 300 AAC Blackout
Length: 8.50"
Material: 4150 CMV steel
Treatment: Black Nitride (QPQ)
Gas System: Pistol-length
Platform: AR-15
Model #: 300P85H50B8R
UPC: 815875019183
(Twist rate, muzzle thread pitch, gas journal diameter, and exact profile may vary by production; verify details to select compatible gas blocks, mounts, and ammunition.)
Frequently Asked Questions
Q: Will this barrel run both subsonic and supersonic ammo?
A: Yes—300 BLK is designed for both. For subs (especially suppressed), an adjustable gas block and tuned buffer often yield the best reliability.
Q: Do I need a special bolt?
A: No. 300 BLK uses a standard 5.56/.223 AR-15 bolt. Be sure your chamber and bolt are properly headspaced.
Q: What magazines should I use?
A: Quality AR-15 magazines work well with 300 BLK. Clearly mark them to prevent mixing 300 BLK and 5.56 ammo.
Q: Is an adjustable gas block required?
A: Not mandatory, but highly recommended—especially for suppressed or subsonic-heavy use—to fine-tune cyclic rate and reduce blowback.
Q: Legal considerations?
A: Know and follow all federal, state, and local laws regarding barrel length, pistol vs. SBR classification, suppressor use, and transport.
Recommended Pairings
Adjustable gas block + pistol-length gas tube
Heavier buffer/spring tuned for your load (sub vs. super) and whether you run suppressed
Free-float M-LOK handguard for accessory placement and consistent harmonics
Quality muzzle device or suppressor interface (verify thread pitch before ordering)
Red dot or low-power variable optic (LPVO) for rapid, versatile sighting
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Shrink your AR without compromising reliability. The Diamondback DB 300 Blackout 8.50" Black Nitride 4150 CMV Barrel delivers a tough, easy-to-clean foundation for compact, tunable builds that run smoothly with both supersonic and subsonic ammunition.
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