Breezie... Timekiller is right, a "significant" amount of your carved-bullet's original diameter got carved away. It was originally at least a 50-something caliber bullet.
The wide conical cavity in your bullet's base shows it was one of the many varieties of Minie-ball. Civil War era Colt revolver bullets and Sharps bullets almost always had a flat "solid" base, and none of them had a wide cavity in the base.
Because the lower half of your bullet's sides have been carved away, we bullet-collectors cannot tell with any certainty what specific variety of civil war era Minie-ball it is. As Relichunters mentioned, it may have been an Confederate-made Enfield, but equally could have been a yankee-made 3-groove Minie whose grooved lower sides got carved away.