Bartlein is a barrel maker owned and operated by shooters who have been involved in barrel making for many years. They built state-of-the-art cut rifling machines which Bartlein says can hold uniform twist rates to the 4th decimal point. Several nationally known benchrest shooters shoot Bartlein barrels. We have Bartlein barrls on many of our own benchrest rifles, and they shoot well. Heavy Varmint Blank 6mm 1.250 inch Tapering to .900 inch 1-14 inch Twist, 29 inch Blank. Weighs: 7.5 lbs. 6 mm Light Varmint Blank 1.200 inch Tapering to .875 inch 1-13.5 inch Twist, 29 inch Blank. Weighs: 7 lbs. 6.5mm Heavy Varmint blank 1.250 inch Tapering to .900 inch 1-8.5 inch Twist, 31 inch Blank. Weig Mfg: Bartlein Barrels SPECS: 22 call land/groove diameter: .218/.224. May require live pilot with appropriate sized pilot. SOLID PILOT MAY NOT FIT. 243/6mm land/groove diameter: .237/.243. 6.5mm land groove diameter: .256/.264.