Everything depends on the individual details of the bullet MD... dimensions, weight, design, etc. There are CW, post-CW, and modern casts which have a varied number of "rings". Once we have some pics and/or some of the specs someone will be far more likely to positively identify your find.
Clean your bullet vigorously. Along the base or within the rings you will probably find "crimp marks" or small vertical lines where it was crimped to a more modern case. Also your bullet is machine made in a more modern process.
It may be 1800s but the very latter part if at all. Its most definatley a post cw projectile
Ok, I appreciate the info. They do look much bigger but someone else mentioned the lines within the groves I looked with a loop and don't see any. Also was it fired or dropped?