Hey there TWS4ewa, I was the Visual Effects Artist on Project One so perhaps I can answer your question.
The trick to selling any effect often lies with stock footage. Stock footage is essentially video of something which can be layered into your footage. In the case of the project one gun effects smoke stock footage was layered on top of the Digital muzzle flashes created with Visionlab.
For Project One I used Solthar's NCC Stock pack which is available to buy here on his website : http://www.nccinema.ch
There are free alternatives, though not of the same quality. You might want to look at the film makers guide
on the forums here for a more comprehensive list of where to get free stock footage.
Those should be of some use to you. Finally, if you're interested in having a look at some of the other Project One effects shots there's a before/after available on my website and here on youtube