Thanks, all, for the input on the tracers.

Lots of helpful knowledge shared here.
Winny, I wasn't sure on the issue mate. I've had many people swear against the spiralling tracers, stating that the effect is down to the camera shake in gun-cam videos. As has been shown, a lot of evidence suggests that this might have added to the effect, but the effect is definately there
To be Devil's advocate, how large can the spiral get? I'd imagine it's a lot smaller for the .303's and gun-cam videos that I've seen would support this.
Thanks in-advance.
I love the contrails too, they look great.
Oleg, are all effects shown 3D?