The 6mm-06 cartridge is a wildcat round, meaning it is not produced by mainstream ammunition manufacturers and usually requires handloading. It is essentially a .30-06 Springfield case necked down to accept a 6mm (.243 caliber) bullet. This configuration provides a higher velocity and flatter trajectory than other cartridges in its class.
This round is primarily used in long-range shooting and big-game hunting. It combines the high case capacity of the .30-06 with the aerodynamic advantages of 6mm bullets, making it suitable for taking down medium to large game at extended ranges. The cartridge's performance is often compared to the more commercially available .240 Weatherby Magnum.
Reloaders and custom gunmakers typically use the 6mm-06 to achieve high velocity and superior ballistic performance but must be mindful of barrel life and potential pressures. It remains a niche choice due to the lack of factory-made cartridges and guns chambered for it.