I just learned that it's not WP in the ammo, it's burning metal. But it seems to behave like WP, so I guess the rule books can be excused
https://en.wikipedia.org/wiki/M202_FLASH
FLASH = "Flame Assault Shoulder.", nice backronym if it's true
https://www.youtube.com/watch?v=LHuDYOVAQYs
https://guns.fandom.com/wiki/M202_FLASH