Here is the full list of all 21 Western 1849 Reloaded achievements.
Complete medium difficulty
Fire 100 bullets in one game
Perform 50 headshots in one game
Kill 6 bandits with one clip
Complete easy difficulty
Complete 3 waves in a row without losing any health
Kill 2000 Bandits
Fire 5000 bullets
Have 2 items equipped in the backpack
Upgrade your equipment 3 times
Perform 500 perfect reloads
Perform 500 head shots
Perform a 15 kill streak
Knock down 250 hats from bandits
Kill 100 bandits using dynamite
Perform 50 Perfect Reloads in one game
Kill 25 bandits in Rage Mode
Shoot 50 canns
Complete hard difficulty
Complete very hard difficulty
Complete insane difficulty