You could be referring to the MG42 which had such a high rate of fire that it made a noise that sounded like a high pitch ripping sound, the only real thing wrong with it (other than the fact the 'bad guys' had it and we didn't.) was that it was made with high tolerances that it was hard to mass produce unlike the Brownings we used at the time.
I believe that no one uses them today, you can contact the History Channel's home page and find programs about German machine guns, some are quite informitive regarding them and the different ones delevoped by Germany during WW II. The Military Channel also has some programs regarding WW II weapons.