Cooper Arms Model 21 in 20 Vartarg. The 20 Vartarg (20 Caliber Vartarg) is a wildcat cartridge based on a modified 221 Fireball case, pushing .204-diameter bullets at high velocity with excellent efficiency. Cooper chambers the Model 21 for this specialized round for customers who want maximum varmint performance from a highly refined, low-recoil package. A boutique offering that showcases Cooper's custom-house roots. Type: Rifle Action: Bolt-Action Caliber: 20 Vartarg Capacity: 1 Year introduced: 1995, USA Weight: 55 oz Overall length: 41.5" Status: Active Intended use: varmint hunting