How to create good muzzle flashes

armagon

Insurgency has very subtle touches that make a great game. One of these touches are the muzzle flashes:

https://www.youtube.com/watch?v=uG4DjX7j7kw

They are really cool, subtle and realistic. How did they do them? Sourced from actual photos? FumeFX?

sprunghunt

It looks like they're using photos of explosions. You can get VFX libraries of images - which is where they probably got these from.