The rules for grenades are woefully incomplete and I secretly dread when players want to use them.
Using RAW, any grenade attack which doesn't meet the threshold of 3 has scatter. To rednblack's question, the amount that scatter is reduced by wireless detonation isn't explicitly defined. An airburst link - a firearms accessory which is
technically separate from the standard functionality which we are describing - says to reduce scatter by 2 meters per hit instead of 1 meter. Normally I just use these rules for all grenade launchers. It effectively eliminates the airburst link as an accessory by making it standard, but the alternative is to basically ignore the line under "Wireless Link" on page 182 that says "This method also reduces scatter," or for the GM to arbitrarily rule how much scatter is reduced.
Separately, this is Ryo's houserule:
Area of Effect attacks
Grenades and area spells can either be aimed at an area (Simple (3) test) or aimed at a specific target (attack roll vs. defense roll.) If you aim at the area, all the targets in the blast radius can (and probably will) use the Run for Your Life interrupt action to escape the blast. If you aim at a specific target, they cannot use this interrupt action; they get their defense roll instead.
I like this better than RAW, but it still has some gaps that can be gamed. For example, technically Run For Your Life can only be used by someone with 1) enough initiative and 2) some movement remaining. Say Achak has IP3 in a combat turn and nobody else does; that means he can fire grenades at an area knowing that people can't use Run For Your Life to avoid them. In my opinion, that would be gaming the turn-based system.
Alternatively, if you fire directly at someone and they roll defense, what exactly does their defense roll mean? That they move away from the blast? If so, by how far? Or does the grenade go sailing past them and miss completely, since they ducked/dodged? If so, but the shooter is using an wireless link to detonate, how far does the grenade travel before exploding? Do you just use scatter rules then, but with the possibility that the grenade will actually explode exactly where you want it, making the defense roll irrelevant? If you're firing directly at someone, does the person they are standing next to (who is going to get caught in the blast if the grenade hits) get a defense roll too? What does
that roll mean? Is the result a can't-miss attack because nobody can roll enough hits to escape the effective blast radius (8-10m) of the grenade?
I think the lack of clarity in the rules, although with the inherently lethality of grenades, is why many GMs and players have a gentleman's agreement to avoid them. I'm not suggesting we do that here, since we all have grenade launchers, but it does mean that rednblack has to make some calls that won't be fully supported by the rules because the rules don't exist.