Here is a picture of a 25x137mm case with the “projectile” in question next to, I believe, a 30x173mm casing.
What is the projectile in the 25mm case, on the left in the photo below? Drill/function dummy? Gun show special?
Source for the photo: https://www.facebook.com/photo.php?fbid=155579072111006&set=gm.269055070694631&type=3&theater&ifg=1
Thanks,
Brian