Thanks Rex! They're not 100%, but really, the tires in the concept are sooooo loose, I'd be modelling just the treads for a week trying to get it as random as that :D haha.
blue gradient from 100% opacity at the top to 0% blue to the center - that layer is set to the blendmode "screen". The same with a red one coming from the bottom.
And this is why i love making weapons, the one thing that is ALWAYS on screen and close up. Very rewarding making something badass that will be seen 100% of the time =)