How do inf guns work?

Here is as far as I got. This is a Smith and Wesson 686 .357 Combat Magnum, in stainless steel.
I got it into Infiltration, and you can actually shoot with it, but it floats out infront of the player without any arm. I extracted all of the arm models from the Beretta model, and I started fitting the hand onto my model, but it is a big pain, and I gave up after messing with it for a while. I think a better way to do it would be to make the grip of my gun fit the grip of the beretta, and keep the trigger geometry the same, so everything just fit. Also, the code for the different guns is worked in to numerous files, so it is difficult to add a new gun cleanly. I wish the system for adding guns was modular, but it is in spaghetti form presently. The Inf team did a great job, but they didn't intend for player addable weapons.
What I have so far is really just a start. For a full gun, you need:
Gun and arm models and animation, including:
Idle, firing, loading, aimed, ready, hipped
Gun on floor model, 3rd person gun carry model
Ammo model
shell casing model
Muzzle flash
Gun code
Bullet model and code
Attachment models, animations, and code.
Loadout info (can't be retrofit, as far as I can see.)
Audio files for everything, clicking, firing, readying, reloading, etc.
And other stuff too!

I started playing with making an attachment instead of a full gun, but this is challenging too.

To get started, it really helps if you have Photoshop, 3DS Max, UTPT, UnrealED. Plus you need to understand meshing, skinning, importing models, animating, and UnrealScript. Not too many people know how to do all of this stuff, and those that do tend to have real jobs and real work to do instead.
I should write a tutorial of how to get as far as I got, at least as a way to remind myself of what I did. If only that cursed Civilization III and Grand Theft Auto 3 were not beckoning me with their siren's charms!

BTW, the original .357 I am using as a reference for this model really has no fluting on the cylinder like this. Some people thought I was too lazy to model the flutes.

And another:

One more:

Oh, and I should mention that the polycount is reasonable too. I forget the exact count, but it is lower than some of the UT guns, and it uses a single texture map 256X256.

Yeah, that is my first skin, first mesh, and first 3DS Max model. I spent way too many hours on it, and started over from scratch a few times. My mesh turned into a haystack of misconnected verticies a few times. But I didn't give up until it was a perfectly clean mesh. But I learned a lot. I could make it in a tenth of the time now that I understand how 3DSMax works.
Oh, one issue that could be a problem: The cylinder should rotate when you cock the hammer or doubleaction fire. The skin I have has countershading built into it, so it wouldn't look good if it turned. Maybe I could fake it by just rotating the front and back plates of the cylinder. The indexing notches wouldn't move, but I don't think it would be too noticable.
Inside of the game, the stainless steel looks completely believable! The lighting brings the chrome sheen to life. It works better than I would have expected.