https://store.steampowered.com/app/2604510/Underrail_Heavy_Duty/

About This Content
This DLC adds three new weapon types - grenade launchers, machine guns and miniguns, as well as a special high-level side mission that will challenge even the most hardcore Underrail veterans.

Key features:

• New skill "Heavy Weapons" which covers two new weapon types - machine guns and miniguns
  
• Grenade launchers, a area of effect type weapon, added to Guns skill
  
• New high-level side mission where you'll fight against elite enemies
  
• New feats