The Marksmen Add-on for Arma 3 has 7 achievements.
Discovered the secret room in Showcase Firing From Vehicles.
Tried all 7 Marksmen DLC weapons.
Completed all official VR Weapon Handling courses.
Completed Showcase Marksmen without injury.
Became the Carrier in official End Game multiplayer for the first time.
Finished any official Marksmen Firing Drill without resting or deploying your weapon (competitive rules).
Finished any official Firing Drill by hitting all targets and spending no more than a single round per target.