It is a misconception that Marines are not allowed to whistle while in uniform, there is no specific regulation against it. The only time it would be forbidden is if it is distracting fellow Marines, and obviously during a combat mission that requires stealth.
The Navy's ballistics expert incorrectly pronounces the brand name Heckler and Koch, he pronounces it "Heckler and Couch" when it is actually pronounced "Heckler and Coke", just like the soft drink. A ballistics expert would not make this mistake, especially one that is in the military, H&K is one of the worlds largest small arms manufacturers, and the U.S. military uses a large variety of H&K models and a great quantity of them.