I'd have to agree with you there Shakken, thats either a flash hider or a conversion to fire test/none-lethal rounds...sim-fire maybe? hard to say which it is, but my money's one one of thouse 3, its definately not a supressor, its not big enough for that, and hey...what would the point be anyway?
And Neo, good work...duh.
EDIT: That could actually allso be a safeguard for the barrel...if you lover a red hot barrel into snow, it wont be happy, that little stump might just remove that nasty little problem.