I can't really tell to well from your pics, but look in the grove and see if you see any lines. That would indicate it is post war as that method of loading ammo didn't come about until after the war.
Speaking as a digger and dealer of civil war bullets for nearly 40 years, I'll testify that no civil war bullets had the version of saucer-shaped bottom seen on your bullet is the bottom-view photo. Your find is a late-1800s-to-20th-Century type of bullet.