One thing I gotta mention here. Relatively new player and playing a version downloaded this June so I don't know if the issue is fixed or if there was something I didn't notice but:

As I was shooting with 'Whirlwind' whenever I quivered sling bullets of undead slaying the game gave me a message something like 'you need a proper launcher for this ammunition..'
No other bullet brand gave me this message, every other brand I was able to sling away. Am I missing something or am I playing with an old version with this particular bug innit?