Leave the base gun as is, but allowing a hop up to change the projectile type to incendiary rounds. Same base damage, but would add the burning DoT to player same as walking over an incendiary grenade. This would then be a nice alternative weapon. Perhaps, an opener at the start of a fight.
The gun reminds me of a flare gun, at any rate.
3 extra rounds would be okay but a total of 5 would be perfect for it. then it can compete with wingman
please do not introduce fire....thats what killed WW2