It is not working for me too.

Hey guys I'm investigating this issue, as I might remove this achievement by tomorrow if its not working properly! thanks for understanding, I'm doing this to give you the opportunity to collect all achievement & if you want to collect kills achievement, open the stats tap on the main menu.

Thank you

Hey guys again sorry for being late to update you, I've deleted the "Gun Pro" achievement because its not working on the latest update unfortunately, the achievement was supposed to be easy.

If you're having any issue with "Weapon Master" achievement, switch to "cold edge" beta from steam properties you'll get to play in a new map but an old update, you get to keep your score and if you upgrade any weapon in "Factory" map you'll get the achievement, know that this work around is because I cant update the game anymore and am sorry for that!

I'll post guides of how to exactly get each achievement, apologies for the confusion.