In the game, switch to camera mode (F8), and then fire up the Mission Editor (F11), and then run the World Editor Inspector (F3). Select your placed weapon, and in the properties in the lower right side (click the Expand All button to reveal them all), locate the Rotates property, and clear it (remove the check mark). Hit Apply. The weapon will not rotate the next time you load the map.
Torque Owner Ken Finney
Tubetti World