It looks like in the latest update the mass now influences projectile damage.

If you set the projectile mass to 0 or 0.00001 it does like 0.1% of the set damage.
If the mass is 0.00010 the projectile drops really fast in front of you.

And even if you set the damage to a really high value (like 100.000.000) it still doesnt do any real damage.

This breaks bullets that should not have any mass (gravity) like lasers.