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