The Marksmen Add-on for Arma 3 has 7 achievements.
Became the Carrier in official End Game multiplayer for the first time.
Completed all official VR Weapon Handling courses.
Discovered the secret room in Showcase Firing From Vehicles.
Completed Showcase Marksmen without injury.
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.
Tried all 7 Marksmen DLC weapons.