Aguila Super Colibri Subsonic Yard Ammo. We call it "Yard Ammo" because it is no louder nor powerful than many air rifles that you can shoot in your back yard. The Super Colibri bullet is only 20 grs in weight and the "Long" case positions it close to the rifling for best accuracy. Velocity is subsonic and just about 590 fps.We tested Super Colibri ammo in a 24 inch 22LR Model 97D Rifle for an afternoon and it worked perfectly. Plinking beverage cans as far out as 30 yards, we found Super Colibri to shoot accurately and quietly, punching holes and knocking the can around. We suggest cleaning with a Hoppes Boresnake every 50 rounds or so. And, semi-autos WILL NOT cycle with such low power. Aguila states that Super Colibri is designed for bolt action and revolver platforms. Otherwise, Super Colibri loads and fires like any other 22LR ammo.Subsonic 22 Ammo is preferred by many small game hunters. The slower velocity is believed to put more "Whack" on small game. It's also preferred by accuracy lovers because it doesn't lose any stability as it slows down (High velocity 22 ammo is known to flutter as it passes through the sound barrier).