well, I know that you can change all guns to a single key but not individual ones or groups. Also, if torp 1 shows as weapon 9, u press button 9 to fire it. If torp 2 shows as weapon 8, u press 8 to fire it. Other wise press the torp button to fire both.

Please correct me if I'm wrong.
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www.geocities.com/lancerpilot/freelancer.html

Okay, I'll try to make this short and accurate.
You can link certain weapons (like ones that have slower velocities, or different torps) by using the "Assign Firing Group" key. Go to 'Options' in main menu, 'Controls,' and 'User Interface' tab @ top. Scroll down to Assign Firing Group (or maybe it's 'Assign Weapons Group') and bind a key to however many different firing groups you want (I use Num 1,2, and 3). Now go to, uh, the far left tab @ top, and assign buttons to Activate Weapons Group 1, ... 2, ...3.
Now, when launch, click (activate) the weapons in your lower right box that you want in Group 1, then press your newly assigned Assign Weapons Group 1 key. do the same for your 2nd and 3rd groups; note, you can have more than three groups, just it's easy to forget which weap is in which group. Once you've assigned a weapon group, you can press your newly assigned Activate Weapons Group keys to switch in b/t them.
~ Lemme know if this doesn't make sense. It really is worth it to have different groups; u can have plasma guns (velocity of 500 m/s) in one group and, say, laser cannons (750 m/s) in another, (maybe even a 3rd group w/all of guns for closer range punch when different velocities don't make much difference ) and switch b/t 'em so your shots are more accurate