> What was the fastest bullet ever fired at sea level?

The fastest recorded bullet-like projectile fired from a portable firearm at sea level reached an astonishing 6,585 feet per second (fps), achieved by the experimental wildcat cartridge known as the .22-.284.

Record-Breaking Small-Arms Cartridges

•    .22-.284 Wildcat (1964): Fired a super-light 15-grain sintered iron projectile at 6,585 fps (roughly Mach 5.8 at sea level) using a modified Winchester case and 50 grains of IMR4227 powder during tests covered by Guns & Ammo magazine.
•    .22 Eargesplitten Loudenboomer (1960s): Created specifically by P.O. Ackley to break the 5,000 fps barrier, it maxed out at 4,600 to 5,210 fps depending on the specific ultra-light load and barrel setup using a necked-down .378 Weatherby Magnum case.
•    .220 Swift (1935): Long held as the fastest commercially produced factory rifle cartridge, capable of clocking up to 4,300 to 4,665 fps with handloaded lightweight bullets, though standard factory loads sit closer to 4,100 fps.

Military and Specialized Kinetic Rounds

•    Steyr IWS 2000 (Anti-Material Rifle): Fires a 15.2mm smoothbore tungsten/depleted uranium Armor-Piercing Fin-Stabilized Discarding Sabot (APFSDS) round at a muzzle velocity of 4,700 to 5,000 fps at sea level.
•    M1 Abrams Tank (120mm Smoothbore): Firing kinetic energy penetrator rounds (like depleted-uranium rods), military main battle tank guns achieve speeds of 5,700 to 6,300 fps at sea level, though these are considered artillery or tank rounds rather than traditional handheld "bullets".