
Ask the Brits.  Enough people have been killed by rubber bullets that they now
use them under only certain "controlled" circumstances.  And they are fired
from something that looks like a tear gas launcher.

There are smaller rubber bullets and pellets (for shotguns).  I understand that
they are only intended to be discouragers, ie. for the snapping but not truly
dangerous animal.  In general, they do not seem capable of really stopping
someone who wants you or past you.  They are fired at very low muzzle velocity
(the .38 ball round is intended for a 400fps load).  Finally, as your mother
warned you, you can put an eye out with that thing.  :-)