The Marksmen Add-on for Arma 3 has 7 achievements.
Completed all official VR Weapon Handling courses.
Tried all 7 Marksmen DLC weapons.
Discovered the secret room in Showcase Firing From Vehicles.
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.