Originally Posted by Ricochet
It is very true however, that players are picky about the BBs they use, and so are certain guns.
I'd say it rests more with the guns than the players themselves. Most are happy to shoot anything that they know works. It's the fact that a lot of BBs don't play well with tightbore barrels, certain custom mods, or with PTWs. The players aren't being picky. They're just being careful to protect their investment. No one wants to use a BB that will jam up and blow their expensive, upgraded mechbox internals to bits.
Seriously, if I show up somewhere and I'm told "You have to use our mystery brand BBs to play here.", I'll be walking away and not playing. I have several "finicky" guns that will only run on Bastards or Madbull Precision. Any other BB I've fed them so far (KSC, Velocity Arms, Airsoft Elite) has resulted in feed issues, jams and / or damage.
So if a player knows that a particular BB works without issue, they will generally use that all the time. And people swear by BB Bastards because they consistently function trouble-free in all guns. I've heard a lot of issues people have with different BB brands, but have yet to hear a single complaint about BB Bastard's product not functioning in someone's gun.