I already posted this in the PC topic, but if you guys aren't aware of it yet, the weapon's stats are only displaying the first 4 lines of text. So if you have weapons or class mods that have more than 4 perks or bonuses to them, you're only seeing the first 4.
A lot of people are pissed off about this and its obviously a major oversight by gearbox. So yea, if you have some neat purple or orange weapons that you don't really see the point of by looking at its weapon card, there may be more to it than it reads.
This issue affects all versions of the game, but there's currently a way to get around it if you have the PC version, I posted the tweak in Stal's topic in the pc forum.