Black Hole Weaponry Barrels employ the use of 416R, match grade stainless steel. BHW Barrels specialize in Polygonal rifling; The shape of the lands and grooves are based on a circle, so there are no sharp corners or edges for the bullet to conform into. This means there is a tight seal and thus less bullet deformation. This rifling form is unique in its ability to allow the bullet to be centered and fully supported by the barrel’s bore.This arc shaped rifling has long been held in very high regard for its accuracy, increased velocity, reduced gas cutting and ease of cleaning. 

Caliber: 5.56x45mm (NATO)

Barrel Length: 18" H-Bar Profile

Gas System: Rifle-Length

Barrel Material: 416 Stainless Steel

Barrel Finish: Matte Black

Rifling: 1:8 Polygonal 3 groove

M4 feed ramp is included

Under Handguard: 0.88 inches

In front of gas block: 0.73 inches

Diameter .750 @ gas block

Threading (TPI): 1/2x28"

Magnetic particle inspections and other non-destructive testing performed on barrels by manufacturer. 

Link to parts manufacturer