Match-grade accuracy - Unprecedented durability - Double-stress relieved 416R stainless steel - Proof Research's steel barrels are produced in-house from double-stress relieved 416R stainless steel. This pre-hardened chromium steel is ideally suited for match grade rifle barrels. Each barrel is drilled contoured and reamed to bore diameter. It is then cut rifled lapped and inspected via borescope. This ensures an extremely consistent and accurate finished product. - Length: 20 Inches - Caliber: 6.5 Grendel - Twist: 1:8 - Threads: 5/8-24 - Contour: Medium - Chrome Lined: No - Gas Block Diameter: 0.75 Inches - Gas System Length: Rifle - M4 Feed Ramps: Yes