Yay, another person who has no idea what they're doing giving advice.
function MyWeaponImage::onFire(%this, %obj, %slot)
{
%proj = parent::onFire(%this, %obj, %slot);
%proj.schedule(1000, "explode");
return %proj;
}
This is by memory, but should explode the projectile created 1000ms after it's launched.
You can store this %proj variable on the %obj or something and then parent the armor::onTrigger function to explode it.