The SB-200 was not only designed for 22 rifle small bore competitors but also for varmint hunters and plinkers. It will easily hold 100 rounds in the down position for easy access during competition. Space in the center is available which can hold up to a 3 50 round boxes. Recently retooled and now fits 17 HMR. The amount each box holds depends on if your ammo came in paper or plastic box originally.Cartridge Sizes:Up to 250 rounds of: 22 Long Rifle 17 Mach 2 22 LongUp to 200 rounds of: 22 Win. Mag. RFUp to 150 rounds of: 17 HMR