Nova Treasure, no offense intended, but I'm fairly certain that the bullet in the photos you posted is a Colt .44 New Model, because the raised ring is quite distinct, and the groove above the ring is clearly square-bottomed. On the Richmond Lab Colt, the raised ring is very indistinct (if visible at all), and the groove is not neat-&-cleanly shaped. That info's source is the Thomas-&-Thomas Handbook's text and photo.
Here's a photo of a no-doubt-about-it Richmond .44 Colt, from the Civil War Bullet Database.
http://www.baymediapro.com/collection/bullet_photo.asp?BID=404&filename=469-1.jpg Click the link for its diameter, length, and other info.