User blog comment:Kogath/Monster Hunter: World Discussion/@comment-6050823-20171107171644/@comment-26808498-20171108225031

Me and my friends speculated that the weapons would have high raw, affinity, and sharpness... but instead of starting at maximum sharpness, it starts at orange/yellow. You can't use whestone to sharpen the weapon. However, attacking with the weapon causes its sharpness to increase. The sharpness will slowly decrease after 5 seconds of not attacking anything.

The idea is that you have to beat the weapon up to increase its sharpness. Just like ner!

No idea what the bowgun does though, we don't gun that often.