Thank you for making and posting the nose-view and base-view photos.
The base-view shows your bullet did have a cavity in the center of its base ...though it appears to be somewhat distorted, perhaps by firing. Therefore, even with the distortion, I think your bullet is an Enfield-Pritchett version. The ruler shows it is an uncommonly long minie ...approximately 1.25" long, even after that hard ramming re-shaped its nose. The only minies which are so lengthy and are .54-to-.58 caliber are Enfield-Pritchett types. See the bullets numbered 219 and 220 in the McKee-&-Mason book on civil war bullets. I am not aware of any specimens of M&M219 and M&M220 coming from yankee-occupied battle trenches or campsites. I can tell you from personal digging experiences that significant quantities of those two types have come from Confederate positions in the Atlanta Campaign ...especially around Kennesaw Mountain.
All of that having been said... both M&M219 and M&M220 are approximately .52" in diameter, when in unfired condition. Please try to get your minie's diameter measured with digital calipers -- or if a ruler is the only measuring tool available to you, give us the closest estimate you can.
