Because you've asked me to comment:
When I don't know the object's ID, I tend not to post. I don't want to merely tell a digger it's not what he thinks/hopes it is.
But, because you asked:
Your bullet is definitely not a Richmond Sharps bullet, for three reasons.
1- The groove on a Richmond sharps is wide and flat-bottomed, not narrow and V-shaped as we see on your bullet.
2- Your bullet's nose is a shorter "cone" than a Richmond Sharps' nose-cone.
3- The Richmond Sharps is .95-inch long, and your bullet is significantly shorter at .795-inch.
When I first saw your post, to help you ID it I looked all through the "Handbook Of Civil War Bullets & Cartridges" (by Thomas-&-Thomas). There is no .52-CALIBER flat-solid-base bullet which matches your bullet's very short nose-cone, groove(s), and length.
That being said... your bullet's nose-cone almost looks like it has been carved down to be shorter than it originally was. Also, it looks like it has been fired, which compressed the gooves somewhat. I thought it might be a Merrill variant, but those are .54, and at least .10 longer than your bullet. The only candidate I can come up with that accounts for your bullet's unusually short length is a whittled-down-nose .52 Spencer that has been fired.