Johnny, here's some info about your "extra-long" minie, in case you don't already know:
Although both sides in the war imported and used the machine-made British Enfield minies, which always have a "plug-cavity" base, only the Confederates made bulletmold-cast ones. So, yours is definitely CS-made.
There was no .54 Enfield rifle. Your "Enfield-pattern" minie was made by the Confederates for use in the imported .54 and .55-caliber Austrian rifles. The CS Army Of Tennessee had many thousands of those rifles. *That is also why a lot of 4-sided-blade Austrian bayonets have been dug in Army Of Tennessee sites, but very few are dug in sites occupied by Lee's army in Virginia.)
Your extra-long Enfield-pattern .54 minie is "mostly" found in 1864-1865 Army Of Tennessee sites. I dug lots of them in Atlanta Campaign sites, and the AoT still had plenty of them in the late-1864 battles around Nashville. I should mention, a good number have been dug at the late-1864/1865 Mobile AL area battles, and the remnants of the AoT still had some when it contested Sherman's march through the Carolinas... particularly at the battle of Bentonville NC.