Instead of completely removing double ammo, because that was a little over the top, try giving 50% more.
Instead of the brace of pistols going from 20 to 40 we do this:
The brace of pistols go from 20 to 30
In this game you can have 4 people fighting for ammo piles and having a character that is based around shooting is going to go out of their way to drain their teammates out of ammo for their own needs.