Ok, now I feel better.

First of all, can you crush the primer of a cartridge hard enough to make it go off? With your earlobe? Remember, the ally *does* have a strength attribute.

Second, guns and inanimate objects most definitely *do* have physical stats. Vehicles, for example, have a Body rating. Other objects have Barrier ratings, and Object Resistance values. Spirits have Body ratings, but they don't get any of the rest. Since they can't actually take on the attributes of the object (barrier rating and so on) they can't get any special properties.

Third, exactly how close do you think a spirit's "physical form" is to what it's imitating? If I have one in the form of a Fairlight Excalibur, does that mean I can use it to surf the matrix? If I have one in the form of an MP laser, can it blast away all day? Or, best of all: I get one in the form of an Ebony credstick, use it to buy a small South Pacific island, and retire. See what I mean?

Just because it *looks* like something, doesn't mean it can *act* like it. For example, the rules are pretty clear that if you give an ally the form of a troll, it still doesn't get Reach bonuses in combat. Rationalize this all you like, but it's not getting any benefits from its form.

Move, yes. Does that mean I can implant cyberware into it? Perform first aid? What about surgery?

Let's not restrict this to allies, then. A Hearth spirit can also appear in the form of a grandfather clock. Sure, it can show whatever time it likes on it's face, since it *looks* just like a grandfather clock. Now, does that mean I can take it apart with a screwdriver? You said it's "mechanically identical". If my ally is in the form of a gun, what happens when I field-strip it?

The magician designs the ally's form, but that doesn't mean that it gets all the properties of that form. If you put a spirit into the form of an eagle, it still cannot fly on it's own wing power, it doesn't get any vision bonuses, or anything else of that nature. And what happens if the mage misses something anatomical? In the book, they give the example of an eagle, but they don't say anywhere that the shaman had to make a zoology roll to design its anatomy properly. The magician doesn't need to know anything about internal organs, either; all he has to do is describe the outward shape, because that's all he's really going to get.

If you want to specifically define they physical properties of an ally, above and beyond what it gets normally, then you can easily enchant whatever you want into an inhabiting focus. If someone enchanted a howitzer to serve as a homoniculi, that'd be fine, although it'd get a mite tricky bringing you ally into restaurants with you. But by default, you can't get the amazing ally who can duplicate anything. You'll have to work it out on your own.