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AR-15 18" Heavy Barrel, 6.5 Grendel Type 2, 1:8 5R, Straight Fluted, Black Nitride

MPN: B6.5MHB18185R(MF)


Premium Grade AR-15 Barrel 18" Heavy, w/ 1:8 5rd Twist, 6.5 Grendel Type 2, Mid Length, Straight Fluted, Black Nitride

Don't forget the AeroShell 33MS Mil Spec Armorer's Grease!

Premium Grade AR-15 Barrel 18" Heavy, W/ 1:8 5R Twist, 6.5 Grendel, Mid Length, Straight Fluted, Black Nitride

100% American made. Barrels are manufactured from two types of steel.

  • 4150 Gun Quality Steel, Heat Treated to RC 28-32 Hardness, and Stress Relieved.
  • 416 Stainless Steel, Heat Treated to RC 28-32 Hardness, and Stress Relieved.


They are Drilled, Reamed, Rifled, Turned, and if Applicable, fluted on CNC Machines. All our Finished Barrels go through a 100% Inspection Process.

Inspections Equipment includes CMMs and Air Gauges for the Bores. Our Barrels are manufactured under the ISO-9002 Quality Systems.

What is 5R Rifling

Conventional rifling uses either 6 or 4 symmetrical lands and grooves on the bullet. Each of the lands (the raised portion of the rifling) are directly opposite one another. Likewise the grooves are opposite of one another. 5R rifling improves upon this by using 5 lands and grooves over the even numbers which puts lands opposite of grooves. Further, the transition from the top of the land to the groove is sloped.

5R reduces projectile deformation as it passes through the bore during the firing sequence. By placing the lands opposite of the grooves, the bullets are no longer squeezed on opposite sides ensuring the projectile stays uniform instead of squeezing material into the grooves. More uniform projectile means better accuracy. Secondly, by sloping the transition to the groove, the barrels become much easier to clean. In a conventionally rifled platform, these corners become depositories for lead and superheated materials left after shooting. Cleaning supplies have a hard time reaching these corners as they are incredibly small. By sloping it, cleaning supplies are easily able to get to the deposits.


Additional Length 18
Profile Heavy
Twist 1:8 5R
Finish Black Nitride
Material 4150 Chrome Moly Vanadium
Thread Pitch 5/8x24
Caliber 6.5 Grendel Type 2
Feed Ramp M4
Flutes Straight Fluted
Gas System Mid Length
Gas Block System 0.750
Gas Hole Diameter 0.086
Charging Style No
SKU ACC-B6.5MHB18185R-MF-32
Country of Manufacture United States
License Requirement None
Manufacturer US Contractor
Mfg. Part Number B6.5MHB18185R(MF)
Caliber/Gauge 6.5 Grendel
Action No
Barrel Length 18
Barrel Twist 1:8 5R
Barrel Bore Type No
Barrel Finish Nitride
Barrel Fluting Straight Fluted
Barrel Profile Heavy
Mount Type No
Beam Color No
Firearm Fit No
Threaded Barrel No
Condition New
Free Shipping No
Weight 2.45 Lbs

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