Gsrxaddict is correct... your long curved lead pieces are from antique plumbing joints in cast-iron pipe. The plumber would first pack the joint with hemp fiber, and then melt lead and pour it into the joint. I was briefly a Plumber's Helper, and when we replaced ancient cast-iron pipes underneath 1800s/early-1900s era houses here in Richmond I've seen those lead pipe-joint seals in real-life. I am 100%-certain that's what your lead finds are.
By the way... the Sgt. Riker website is incorrect... the photos show the brass sabot from a yankee 10-pounder (2.9"/3"-caliber) Parrott shell. That is absolutely NOT a Read shell's sabot.
Also, Read shell sabots are most frequently wrought-iron, less frequently copper, and only a few made of brass. (Brass was scarce in the Confederacy, and so it was saved for making things which would get used more than once... an artillery shell sabot only gets used once and then it's gone.)