Well, it's not super-duper accurate either, but there isn't any function on the weapon to improve accuracy as yet.
Traveller sources [mostly CTT Book 4: Mercenary] tells us that the TL 13 Gauss Rifle magnets impart spin on a flechette, which provides the accuracy need without the flechette having to contact the barrel. This prototype weapon is simply throwing a .50 cal. [one-half inch] slug downrange.
But as Ian points out, the great-great-grandchildren of the GR-1 will be the sci-fi guns of the future.
Now if we could just get the fusion thing dealt with....