Namxat asked:
Find them unfortunately often along with fragments of driving bands (is that correct in English for the copper band that takes up the rifling?).
Yes, "driving-band" is the correct term in the 20th Century. In the 1800s, the Ordnance Department (and artilleryman's) term for the metal ring on the body of an artillery projectile which "took the rifling grooves" was sabot... and that term is still sometimes used today.