Lets look a little closer at it.
1.Its not planes as butterfingers said it looks just as good from the side so it must be either boxes or spheres, assuming its flak.
2.As far as I know you cant have multiple firespots,you can have two certainly with dual wield.
3.Flak tends to have a wide range of damage so would injure both player and enemies if used at close range.
The best way to do this though is with flak, spheres or boxes with a transparent alpha channeled texture,the fireloop would have to be set pretty high in the gunspec with the lifespan set low in the flakspec so the flame didnt get too far from the muzzle.
Reload quantity would be infinite.
The odd thing is that in weapons that use flak such as the bazooka,the gunspec has a damage value of 100 and the flakspec has a damage value of 50,considering its the flak that does the damage I dont know why the gunspec has this value,but if you shoot at a nearby wall or the floor you will see that there is a large damage radius and personally I have found no way to reduce this.
You can set exponhit to 0 and use plyrdistwithin to inflict damage.
I have also been unable to change the explode decal in the flakspec even by changing exponfloor and expinair to other decals,seems to have no effect.
It may be that butters used a scaled up custom muzzleflash with a high fireloop to get that effect but I doubt it,it looks so much better than that.
Anyway if your looking to create a fireball flak is the way to go and you could even add a little spice to it using spin, weight, speed etc and the inability to change the explode decal on contact wont be an issue.
