Something thats been bugging me...

Well of course we all know, Gandiva, Yoichi, etc, are great weapons, along with their marksmanship counterparts. I myself am working on gandiva lately, but while looking at trials something caught my eye, and i just dont know what to think. There are ranged weapons on the multi-hit path, from what i saw, one was for double attack which "occasionally does double damage". However there are still "Occasionally attacks 2-4 times." and well...

Im curious, has anyone made one of these? How do they work exactly? Does it consume extra ammo? does it show multiple impacts? Or is it like barrage? I cant imagine where/when it would be a useful weapon persay, but it is something that ive been wondering about.