Are you sure it's a gun and not a funboard?
anyway - there is a mentality shift between longboarders and shortboarders many times.. shortboarders tend to be younger, more aggressive, a higher population percentage of kooks (just because media-wise, a shortboard is 'cooler'), and so on.
Now, I grew up a shortboarder, so hopefully no one gets all defensive on me.
Longboarders typically are older and more relaxed. There are younger kids into longboarding, but not as many as those that go the shortboard route.
The biggest issue typically is that longboarders can catch a wave earlier, so we all sit further outside than the shortboarders. Therefore, we usually are already up on a wave when a shortboarder is paddling for it and they either have to pull back or (many times) they drop in on us, and after a few times, arguments start "you're stealing all the waves", "well stop dropping in and I'll give you some" and so forth.
Also, being further inside, shortboarders many times are just sitting right in the way and don't move when longboarders are obviously paddling for a wave.