BudsGunShop.com - 5 or 6 grooves?

5 Grove Semi-automatic gas impingement system. Flat top type upper receiver. Forged 7075 T6 aircraft aluminum receiver with aluminum trigger guard. Hardcoat black anodize finish. Carpenter 158 steel bolt. Sixteen"
4150 chrome moly vanadium 11595E steel heavy profile chrome lined barrel with A2 flash suppressor. 1 in 7" right hand twist. Six position telescoping buttstock with Windham Weaponry logo. M4 double heat shield handguards. A2 black plastic grip. No sights. Ready for optics or other accessory sights on Mil Std 1913 Rail. Mil Std 1913 rail gas block. 6.15 pounds (without magazine) / 36.125 inches (32.375 inches with telestock collapsed). Hard plastic gun case with black web sling and operators manual.
Barrel Length : 16
Caliber : .300 AAC Blackout
Capacity : 30
Finish : Black
Item Description : WWE 300 BLACKOUT 16 DBL BLK 30

Eve, this rifle has a 16" Heavy Profile Chrome Lined Barrel with with 5 lands & grooves, A2 flash hider - Barrel is made from 4150 Chrome Moly Vanadium 11595E Steel and has a 1:7" Right Hand Twist.