Well, seeing how you exaggerate with the distances (which map did you see a 300m kill? The longest kill I've ever got was 225m, and that was a looong shot), I'm pretty sure you exaggerate with the percentage as well.
Also, as far as I remember - you don't get the distances shown when you spectate, but I might be wrong on this one.
I've gotten a one shot rifle kill on a moving target on the large park map from something like 240m. There are a few maps where 300m is possible, but ... yeah, that does seem a bit outlandish.