The key to enchanting or using any magic in The Dresden Files is to think about how it works. The easier it is to understand, the easier it is to implement.
For example: Harry's Shield Bracelet is just that, a shield, a barrier of energy that stops forces cold. Simple, relatively.
The more complicated the system, the more difficult it is to implement magically, the more energy it uses and (typically) the more effective it can potentially be. Enchanting in TDF means that you are creating a permanent system of magic. Either it is a permanent working of energy that augments the item or it is a ground work of "Circuitry" waiting for power.
The Wardens' Silver Swords are permanent systems. But a Sword is a very simple item, a flatten piece of metal with an edge. You can sink that magical system into the metal of the blade and all it does is make the blade sharper and stick around while it disrupts enchantments.
Harry's Rings are a more sophisicated example because they too are a system that continuously maintains itself.
Harry's Bracelet is an example of Magical Circuitry. Harry's Bracelet by itself is just that, a Bracelet. When he pumps magic through it, he gets the desired shield. Same with a computer.
I would recommend in the game that a character need a high academics/mechanics score to be able to make more complex items because you need to now how the item works. You need to be able to answer, "What is the permanent magic doing?" or "What does a magic gun do?" Harry's rings are a battery, Harry's Bracelet a a bit more complicated, a Warden's Sword is merely augmented.
Modifying a gun, you can enchant either the gun or the bullets. Enchanting bullets would be easier, but they would be disposable and if not handle with care very expensive to replace regularly. But, both bullets and guns could be done with creativity to a point.
"What do Magic Bullets do?" The easiest thing to do, In my mind, to bullets magically is to make them indestructible or close to it. Making sure the bullet doesn't break on impact would cause less damage, but you could collect them later and save money. The other thing you could do easy is make Harry's force ring into a bullet. It would be more difficult to implement (and you'd risk blowing yourself up) but you could get one hell of a one-shot pistol grenade. You could even charge it easy too: Make the charger out of a 9 volt battery or the equivalent (Thaumaturgy links) then attach it to the bottom of a rollar coaster car at a local amusement park.
You could also inscribe Magic circuitry into the bullets for coatings like fire or electricity. But, those systems might not even work.
(Would also work great if not better with Arrows)
The best guns to use are the simplest, the ones with the least number of moving parts. Revolvers and double-barrel shotguns in this case are the ones, but if you want an automatic, go with a glock (Only has 22 moving parts) or if you want old school wizard, a Musket.
"What do magic guns do?"
A Magical suppressor inscribed on the barrel would be the simplest. But, the only thing you could really do to a gun magically would be to make the bullets go faster, go farther or (if you really wanted to mess with the CSI guys) make them go in a straight line.
Magical computers just can't work. Not because "It is technology, therefore it cannot work around a Wizard" but because of the magnetics. I've honestly thought about telling you you would need to Macguyver a motherboard and make computer components that run on magic and you would need to be a sensitive, but in the end it comes down to Magnetics. The Hardware of a PC can be duplicated, but the software cannot be. Wizards wipe magnetic storage devices and therefore could not be in the vicinity of a normal hard drive let alone tiny magnetic devices such as Processors with BIOS on them. Without the ability to store and access information, a computer cannot work. Therefore, no magic computers.
Although if I were a wizard I would just get a really long extension cord and go through a lot of mice and keyboards if not make a keyboard out of a typewriter and Macguyver a Trackball.
That's all I got at this wee hour on this subject.
