Here is the full list of all 21 Western 1849 Reloaded achievements.
Complete medium difficulty
Fire 100 bullets in one game
Upgrade your equipment 3 times
Perform 50 headshots in one game
Complete easy difficulty
Kill 6 bandits with one clip
Kill 2000 Bandits
Fire 5000 bullets
Have 2 items equipped in the backpack
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
Complete 3 waves in a row without losing any health
Shoot 50 canns
Complete hard difficulty
Complete very hard difficulty
Complete insane difficulty