I am creating a mage with the spells

Demolish Ammunition, Demolish Cybernetics and, Demolish Electronics.

Demolish [Object] (Direct, Area)
Type: P • Range: LOS (A) • Damage: P • Duration: I • DV: (F÷2)+2
These variants of Shatter/Powerbolt/Powerball (p. 197, SR4) only work against a specific inanimate object. Each different
type of object requires a separate spell: Ram Door, Wreck Vehicle, Demolish Gun, and so on.

As per the rules the demolish spell is a "targetted Powerbolt" type effect where nothing else is harmed in the area save for the type of object being affected.

The Demolish spell is "direct" and affects inanimate objects from the inside out so no resistance tests are allowed from armor and since they have no inherent mana link they cannot get any kind of willpower type test either. The only test needed is a success test by the caster to overcome the object resistance test (p. 174 SR4)

All of the above items affected would be a 4 or higher target number since they are all complex, highly machined, and processed inanimate objects.

Now my question is, how much damage would be needed to demolish say a few clips of ammo or a cyber arm and wired reflexes or what have you?

The barrier ratings (p. 157 SR4) listed do not really cover smaller items or materials that are used to create bullets, electronics, or cyberware. Also, the structure rating listed is for destroying a 1 meter square of the substance that is 10cm (4 inches) thick. Not nearly as much material is included in one or even 20 clips of ammo, Maybe a heavily cybered up street samurai with a ton of bone lacing and dermal plating would have the equivalent of a 1 meter square, 4 inch thick plate of densiplast or a metal beam.

Has anyone dealt with this spell before? How did you and your GM work it out? If not, what ruling would you make?

Thanks for your help!

Keep in mind that the spell requires Line of Sight to the target and visual targeting modifiers might apply. This would make Demolish Ammunition quite difficult in most situations.

As to Demolish Cyberware there are a few ways to take it. In general I would not allow the targeting of cyberware independently of the living target that the cyberware is a part of. However, if you and your GM are open to it, then the spell could certainly be effective. Again, keep in mind that you'd need LOS to the cyberware that you are targeting (So wired reflexes wouldn't be a valid target, but a cyberarm or cybereyes would be.)

As to how much structure any of these things would have my opinion would be in the 1-4 range (though larger electronic structures might have more.) I'd suggest basing it on their size and how difficult they are to break compared to doors, drywall and plaster. If about the level of glass then go low and if tougher then perhaps around the same as the doors/plaster level even if much smaller. I'd err on the side of less structure for small objects if your GM wants the spell to ever actually be efective.

I had not thought of it that way. I always thought if the caster could see the center he or she targeted for an area spell (which Demolish is) it did it's thing within the area and the caster didn't have to see each and every target within it. Like a Powerball detonating in a hallway I would think it damages everything in its area of effect. If a desk was in the area I would think all the papers and such inside the drawers would be equally as damaged and not left alone because the caster could not see them. Or in the case of someone hiding around a corner, would a the Powerball blasting the area that encompassed that corner affect that person as well?

As per the Area Spell rule it says: "Area spells affect all valid targets within the radius of effect"
but it also says: "All visible targets within the area are affected"

So does that mean an invisible creature in the middle of a Powerball area blast remains untouched? Are the desk drawer items in the above example undamaged? I know Powerball is a "direct combat" spell. Does that imply that any direct combat area spell targets everything valid and visible or everything valid regardless of visibility?

Which is the correct way to handle a direct combat area spell?

To affect some one or something you must have line of site, except for indirect combat spells wich work differently and would effect everything in the area.
That being said, sometimes a grenade is better than a spell.

The correct way is _not_ the way you describe in the first paragraph but rather the way that you imply in at the end of the third: that it effects only valid and visible targets. This is one of the key differences between direct and indirect combat spells. Both do damage, but direct spells can only target that which the caster can see while indirects can hit anything.

Thus, you can cast a fireball at a corner and hit people within the spell's radius who are out-of-sight around that corner, but a manaball cast at the same corner wouldn't hit them.

Excellent! Thank you for the clarification!

Just takes an acid area spell limited to weapons and you are set. I imagine it's pretty common for lone star mages.

No, they just use fireballs limited to criminals. Trials are expensive.

I had a low-level mage with an area demolish guns spell. We considered guns to be "manufactured high tech", so any time I rolled three hits on a spellcasting test, all the guns I could see (whether I liked it or not) would cease to function - Unless the gun was on the person of someone who was protected with counterspelling. Then, I usually failed. Yes, one could argue that "no, he wasn't providing counterspelling to the gun itself", but that would be pretty dumb, since that spell is so easy.

Collateral damage looks real bad when it comes time to get your contract re-evaluated.

I had a player once who took demolish clothes. Turns out it's a great spell, need to lower an enemies moral and make them retreat/give up? Need a very good distraction? Want to be the life of the party? It's surprisingly useful.