I recently watched the movie Fury, and in one scene, Brad Pitt and his platoon of Shermans go up against several Anti-tank guns, possibly Pak 40s. When the Paks began to fire, the shells made a very distinct "whistling". Brad Pitt explains that they're firing High Velocity rounds (APCR?) Is there any truth to this? What causes the whistling, and where can I find out more? I tried looking it up to no avail. I would also provide a link to the scene, but there is no clip containing that I can find that shows it.
high-velocity rounds break the sound barrier, and size (diameter) of shell and velocity determine the sound. Lots of WWII veterans talked/wrote about the sounds made by different munitions; heavy artillery sounds like a freight train, antitank shells scream, rockets moan, and mortars sounded to me (Iraq, Afghanistan) almost like a creepy whisper, although there must be a better way to describe it. Some modern tank guns, which fire hyper-velocity rounds, make an spooky, very deep 'woo - woo - woo' sound. Small arms bullets crack as they go past your head; they only make the 'zing' and 'beoww' sounds (as in bad movies) when they ricochet of something.
Fury is too new to be on youtube yet. Check out Band of Brothers episodes about Bastogne, or The Pacific episode about being shelled at Guadalcanal, although these are mostly heavy artillery versus tanks shell noises.