Erhm.. if that is your position it is 3km up in air?
[2898.221436,17.397015,2868.661133] = x,y,z
Assuming that the last number is wrong, the proper coordinates are: [2898.221436,17.397015,0]
In the script, use:
weapon = "weaponHolder" createVehicle [2898.221436,17.397015,0.25];
weapon addWeaponCargo ["AK74",1];
That should work.