Identifying mangled fired bullets if difficult to do with certainty. But it does look like a civil war era Colt .44 "New Model" bullet. Identifying characteristics for that version of .44 bullet are: a single body-groove above a recessed base, which is flat and solid. Supporting that ID of your bullet... the .44 Colt Revolver of that era had seven-groove rifling, which seems to be the count extrapolated from the undamaged side of your bullet.