Make reagent-infused bullets 'leak' the reagent.

[BadClown]

Bullets actually already work this way, it's just not... consistent. Sometimes the bullets won't always inject their chemicals, and some chemicals don't inject at all. It's more than likely a bug.

It seems that bullets treat the reagent as if it was applied to the skin, and thus the reagent can be blocked via protection (someone wearing a gas-mask isn't afflicted by a sarin-infused bullet). Where as if the bullet is inside your body, it should be applied as if it were injected.