Rio Ammunition Royal Buck 12 Gauge 2.75 in Size 4 Buck Shot Ammo 25 Rounds. 75 in Size 4 Buck Shot Ammunition online at OpticsPlanet. This RIO Ammunition Ammunition features 4 buck shotgun shells that deliver powerful stopping power flawless precision and reliability for large game medium game. With premium plastic shotgun shells equipped with lead you ll deliver hard-hitting muzzle velocity. Buy now to get 2 3/4 in shells delivered right to your door. With daily deals on Ammunition and other high-quality shotgun ammo from trusted brands like RIO Ammunition you re sure to find the ideal effectiveness for your next hunting trip or range visit. Stock up today to save big on shells and other top-tier tactical hunting and outdoor gear at OpticsPlanet. What is Rio Ammunition Royal Buck 12 Gauge 2.75 in Size 4 Buck Shot Ammunition good for? The manufacturer suggests that it is good for large game medium game.