Airsoft is about as real as it gets when it comes to Military Simulation (MilSim).
ArmA: Task Force 121
Join Task Force 121 ArmA 3 MilSim. We are a semi-realism group that does operations 4 times a week. We will train you to become a fighter in the 75h regiment or if you have prior military training you can join Combat Applications Group (CAG) and become an elite fighter.