The stinger that shoot the "swirly bullets" has what's called the barrel3_twisted.
In Borderlands, all guns are created by a generator that follows various rules using various gun parts to create that gun you are using.
The barrel3_twisted's main benefit is that it adds additional [elemental] tech for elemental stingers (when elemental the bullets do not swirl).
Sadly on a non-elemental stinger the twisted_barrel is really, well, useless, & actually detrimental.
I'll admit it looks cool, but it's really just crap.
Yeah, not that exciting sadly.
One thing about Borderlands is the amount of detail in the items.
It's just incredible when you begin to understand it.
Once you understand the basics behind the COM/shield/gun generation system, it can become extremely addictive as you then have a never-ending quest to find the perfect gun, with the perfect combination of parts, etc.
That is why people like myself have put in insane amounts of time into farming in the game for such items...
The simple charm of the game once you've gotten into it combined with the most amazing weapon generation system ever created in a game (arguably) can make for a lot of hours spent, though admittedly not for everyone.
I highly suggest venturing into the official Borderlands forums if you want to learn more about the game, as the amount of information there is just amazing, & while less active now, there is still a great community of people far more knowledgeable than myself that still post there.
For newbies, this might be rather overwhelming, but if you are curious about how the generation system works, here are some VERY good reads.
http://gbxforums.gearboxsoftware.com/showpost.php?p=2063812&postcount=1
http://gbxforums.gearboxsoftware.com/showthread.php?t=86935&highlight=parts+picker
Gear Calc allows you to play with making your own gun, etc, though sadly the creator has not been around to update it to level 69.
http://blmodding.wikidot.com/gear-calculator
The Wiki is filled with a lot of incorrect information, so i always recommend the forums for accurate info, but there is some good general info on there, like this section detailing COMs.
http://borderlands.wikia.com/wiki/Class_Mod
Also, if anyone is up for playing on PC, i'm usually up to play some Co-op.
Steam: sardonicn7
Xfire: n7dgs
Gamespy: ense7en