LRP guns

I’d be interested to hear how the various systems handle guns from both flintlocks to machine guns, to sci-fi weaponry.
[ul]How do you handle them in your games?
What rules do you have?
Do you use a projectile weapon of some sort?
If you do where do you get them from?
What treatment have you had from the police?
Is there any advice you can give me on liaising with them?
[/ul]
thanks in advance