You’re right, Waseem... The challenge seems to be glitched. For some players, it only works during the Nile Guard mission and only when using the main tank shells, then switching to knife-only or pistol-only (other challenge) Plenty of players on Reddit & Steam have reported the same issue and Nile Guard is the only mission that seems to work
There is a part of this mission where you need to fire from a MG on a vehicle to protect the President, not sure if that counts against this but I didn't get the challenge completed
