Weapon/refining materials

I am a new player that is using the bone shooter HBG. To upgrade it to grade 6 I need these parts. I can get it from the story mode but my question is if these materials are ONLY for the bone shooter > grade 6 or for EVERY weapon to go from 5>6 if so it would be best to save it for a better weapon?

Also what hbg would yall recommend to spec in (most dps)

Thanks!