An ill-defined term with at least two distinct usages. The older usage was for rifle calibers of .30 or greater used by standard military rifles of WWII and before. But this term can also refer to any centerfire cartridge whose design allows it to handle much greater pressures than rimfire calibers. Thus a .223 centerfire rifle cartridge is vastly more powerful than a .22 rimfire although their bullet width is virtually the same. Centerfire projectiles move in the range of 2400 feet per second or about 1600 miles per hour.
