These bullets were made to hide their carbide rear end inside the cartridge. They were designed to be given to the Afghans during the Soviet invasion to create barrel obstructions in enemy rifles.
Heard about them from this video (6:34). There doesn’t seem to be much in terms of English language sources, from my brief searching, so if anyone finds more info please share.
It always be like that. You just never know if this round will blow up your barrel, leave no dirt or just be normal.