Cooper Arms Model 21 in 204 Ruger. When Ruger and Hornady introduced the 204 Ruger in 2004, Cooper was among the first custom makers to chamber for it. The Model 21's short action is a near-perfect fit for the cartridge's overall length. Delivers exceptional velocity for a .204-diameter bullet with minimal barrel wear compared to the 17 Remington, making it a practical long-range varmint choice. Type: Rifle Action: Bolt-Action Caliber: 204 Ruger Capacity: 1 Year introduced: 2004, USA Weight: 56 oz Overall length: 41.5" Status: Active Intended use: varmint hunting, target shooting