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