Many missiles, grenades, and some guns create an explosion when they hit. When working out the effects of a Blast weapon, anyone within the weapon’s blast radius in metres (the number in parenthesis) is also hit. Roll Hit Location and Damage individually for each person affected by the blast.
Keep scatter rolls to indirect fire for the most part.
If a direct fire blast misses but has no degrees of failure, use common sense. Do a vertical scatter, if it hits the ground near their feet they might still take damage.
If they have a height advantage and are essentially looking down on the target, regular scatter might apply. 1d5 or 1d10m further per degree of failure?
If there are obstacles nearby behind the target that the explosive would detonate on, make it happen.