Designing FPS Weapons

For the final tak of the year I need to design, model, texture (and show in a working game engine) a gun which would be suitable for use in current generation FPS (First Person Shooter) games.

I've decided to model a shotgun. It was an easy choice considereing I've already designed an assault rifle, pistol and bazooka for another course, creative thinking. Designing a shotgun allows me to come up with some new ideas.

For the general concept of how guns function I looked at the Principles of Firearms. This webpage names the components of a gun and describes their function. This is useful as this gives a list of what I need to include in the design.
http://rkba.org/guns/principles/definitions/gun-components.html

I also looked at an article on specifically how shotguns work and what defines them from other types of guns. This is essential to understand if I want to design a shotgun that looks like it could work.
http://science.howstuffworks.com/shotgun1.htm

Some interesting things I'm noting are:

1.The size of the barrel indicates the gauge number and therefore, the amount of recoil firing will have. The lower the gauge, the wider the barrel, the higher the recoil.

Here are two examples:

This is a 4 Gauge shotgun with a relatively wide barrel and will have lots of recoil.

 This is a 20 Gauge shotgun. As can be seen, it has a thinner and longer barrel than the 4 gauge one above. This will have less recoil, which is safer for the user, but doesn;t look as cool.

A 4 gauge shotgun may seem to have too much recoil but having a fair amount makes the gun look much more powerful when fired.

2. How will the shotgun be reloaded?
There are 4 main types of reloading a shotgun:
Break action - Where the shotgun 'breaks' open and allows the cartridges to be reloaded into the barrel manually.
Bolt action - a bolt on the shotgun is pulled to release the remains of the last cartridge and allow a new one to be loaded.
Pump action - probably the most famous form of reloading, this is where a fore-end (pump) is placed under the barrel, pumping back and forth once reloads the gun. It also has a recognisable sound.
Autoloaders - These function similarily to machine guns and will automatically reload with no input from the user.

To keep with my current theme of designing things to fit in with the world created by the Heroes and Villains assignment for creative thinking, similar colour schemes and designs will be used.






References:
Image of 4 Gauge shotgun
http://media.beta.photobucket.com/user/Sn1P3rM98/media/ks23.jpg.html?filters[term]=4%20gauge%20shotgun&filters[primary]=images#/user/Muskyhunter1/media/Hunting2008151.jpg.html?filters%5Bterm%5D=4%20gauge%20shotgun&filters%5Bprimary%5D=images&_suid=136059626497905193423193835687

Image of 20 gauge Shotgun