I was playing around and fixing stuff in existing bullet projectile function and this is what i've got
Looks pretty ok, will need some more tweaking but atm it was fastest solution that actually worked very nicely.
How to?
1. I used a texture of a bullet for a projectile, fired it normally as i did before.
2. Used a second texture that fires and has range up to 8 meters infront of marine and imitates smoke, or a bullet trail, it also grows so it feels like the smoke is dissipating as well as going transparent.
Pretty happy with the result, improvement to this would be writting a shaders that dissipates smoke really well, but that's out of my league xD