Must be something embedded throughout the entire file.
Hmm interesting link, I had no idea. But I did get those sounds to work without looping using a workaround. I just opened a non-looping Q2 sound in windows SoundRecorder and inserted the custom wav at the begining. I then chopped it off and saved it and did the same for the rest of those machinegun bullet sounds. (They now are 22khz because I inserted them into a 22khz sound, but of course you could do the same thing and insert them into a 44khz non-looping sound).