Warface: Breakout

Don't forget, this applies to your teammates as well. So the easiest way you could do this is to play with your buddy and let him drop you a gun.

I can confirm this carries across rounds. So if you pick up a weapon and the round ends, you do not need to pick up another weapon.

A few tips to get this quicker:
1. The LMGs are broken in this game. It's the priciest weapon in the Assault Rifles menu.
2. It helps to flank the enemy so you have an easier time picking up kills. So pull out your knife and run along the edges of the map and look for easy kills.
3. The time-limited team deathmatch, that is live now until 21st of March 2021, is a good opportunity for this achievement as it's more chaotic and you can get kills more easier.
4. In the bomb mode, the easiest kills are acquired when you are either waiting for somebody to plant the bomb or for somebody to defuse the bomb.

Good luck! :-)