It is recommended to use it in offline mode.
I just tested the Unlimited Ammo for Bowguns.
It seems like the only thing I get unlimited from this cheat, is the special ammo like Wyernsheart (machine gun shot) from the heavy bow gun. Doesn't work for the light bow gun with their special ammo (mines) and neither does it give unlimited ammo from the other ammo types.
There are a lot of different weapons and ammo combinations and so we may have to make multiple options for them. Again, savegames with a nice explanation of what is NOT working would be very helpful.