While Helldivers 2 has a familiar, XP-based levelling system, you unlock new weapons by spending Medals on reward passes.
You get Medals from simply completing missions and operations, with higher difficulties offering more Medals.
– G-6 Frag: Low-damage, short-fuse grenade - 2 Medal – SG-8 Punisher: Pump shotgun – 4 Medal – P-19 Redeemer: Rapid-fire machine pistol – 5 Medal
– R-63 Diligence: Marksman rifle – 8 Medal – SMG -37 Defender: Slow-firing sub-machine gun – 15 Medal – SG-225 Breaker: Rapid-fire, magazine-fed shotgun – 20 Medal
– G-16 Impact: High-damage grenade that explodes on impact – 20 Medal – LAS-5 Scythe: Laser beam weapon – 30 Medal
– SG-8S Slugger: Slug-firing Punisher variant – 60 Medal – SG-225SP Breaker Spray&Pray: Drum-magazine Breaker variant – 60 Medal – PLAS-1 Scorcher: Explosive energy weapon – 75 Medal