What specific type of rubber or plastic do people use when making rubber bullets?

Question

Need a type of specific rubber or plastic for this one please, not just rubber in bullets like wood on boats, a really specific type.

Answer 1

"Rubber bullets" seems to have become a generic term for everything from rubber-coated steel to solid rubber or plastic. The only specific material I found in a short search was polyvinyl chloride, a fairly soft plastic. Even these can be lethal.