Long Weapon Progression

Was checking my stats on tracker.gg. I have 4+ hours with a gun but it is just now at level 20. Is it really 8hours per gun just to get all the attachments? That seems crazy! I played 3 games the other night and only went up 2 levels, that seems incredibly slow even with the recent changes.

I play breakthrough and get anywhere from 30-50 kills a game and play objective. Does this feel slow to everyone else or just me?