I saw a post about wood plugs in the base or Enfield rifle bullets. Then I saw this video. American bullets on the Union side had metal plunger solutions in large part I learn. In the south the base was just hollow with expandable cuts in the outside rim like what I have been used to in firing my reproduction Enfield. Bullets weren't grooved on the outside of the hollow bullet base generally so the plug, in various versions, expanded the base of the bullet into the rifling of the barrel. However, I found this video that tells more about the development of bullets for military long arms of the mid 1850's. There were several methods tried in the day of manufacturing bullets and rifles without being capable yet of mass production fine tolerances. The various solutions I wasn't aware of at all. I thought a minie bullet was a minie bullet.
https://www.youtube.com/watch?v=zJ9X-6sFNHc
Civil War Enfield bullets
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