Here is the full list of all 26 Reign of Bullets achievements.
Reach level 100 in the Survival mode
Equip 10 epic weapons on your ship
Reach level 70 in the Survival mode
Loot a total of 100,000 scrap
Use the shield to absorb a total of 50,000 damage
Spend a total of 1,000,000 scrap on ship improvements
Clear a level with only 1 HP remaining
Defeat a boss with ony 1 HP remaining
Reach level 50 in the Survival mode
Complete level 31 to 40 with an S-rank
Complete all 40 levels with an S-rank
Have 10 available weapon slots on your ship
Complete level 21 to 30 with an S-rank
Wreck Titan Enforcer, the multi layered, screen filling, AI droid
Loot a total of 10,000 scrap
Spend a total of 100,000, scrap on ship improvements
Sink Drydock, the weaponized submarine, crab cyborg
Complete level 11 to 20 with an S-rank
Clear a level on the highest difficulty
Take down Daisy, the ill-tempered, trainpulling, desert worm
Have 5 available weapon slots on your ship
Spend a total of 10,000 scrap on ship improvements
Complete level 1 to 10 with an S-rank
Loot a total of 1,000 scrap
Kill a boss without having weapons equipped
Shoot down Edelweiss, the flying tank dispatcher