Guild Wars 2

I randomly get progress in weapon master achievements.
Few days ago I noticed my staff weapon master appeared in achievements close to completion. I looked at it from time to time and it seemed to grow a little every now and then. I though to myself that maybe it reads my longbow/great sword as staff so I killed group of ~7 enemies and got +1 to achievement progress so not exactly.
Now I got first tier hammer achievement even though Im still only using lb/gs. It seems to grow by itself from time to time.
- both times I was without party
- once I was in open world, other time I was in story instance
- never saw anyone nearby wielding corresponding weapons – players and npc alike
- I play ordinary ranger(no druid)
- first I completed 5k staff kills, then got 100 hammer kills

In the early days, my Staff Master increased whenever using a canon in WvW. Not sure what’s causing your hammer master to increase though.

There are some transforms that count towards certain weapons where the <X> Master achievements are concerned, maybe the same is true of some damage-dealing utility skills?

The Notes and Discussion on this page explain some of the odd behaviors with Weapon Master:
Example – Kills performed by a ranger’s pets for example, count as Greatsword kills, while necromancer minions count as Hammer or Scepter kills.

https://wiki.guildwars2.com/wiki/Weapon_Master

Not a bug. Good luck.

Well, I’d say “is a bug, but not one that is going to get fixed”, rather. Because it’s … certainly not a feature.