After fiddling with the firearms rules for my character, I've come up with some suggested changes, which make a good compromise between playability and realism.

• Magazine size - Allow all guns to have variable magazines, ranging from 10 (for pistols), 20, 32, 40, and 50 round magazines. Increasing magazine size by more than 25% adds +1 to Concealability modifier. Quick and dirty rule, as currently, the only way to increase ammo capacity costs 500 Y and increases capacity by 25%.
• SMG Damage - At present, it appears that the future trend is towards high velocity, small-caliber rounds which are more effective at penetrating armor. SMGs can do Damage 4P, AP -2.
• SMG Range - High velocity PDWs should have slightly better range than typical SMGs. Possibly 0-15, 16-60, 61-120, 121-200.
• Weapon families - Some classes of weapons (i.e. ARs and LMGs) should have interchangeable ammo. As do some SMGs and heavy pistols.
• Carbines - Rifle damage, Concealability +5, Range 20% less than rifle. Essentially, a Rifle with the Barrel Reduction mod.
• Gas Vents - Should be removable and replaceable. I think the game designers must be a bit confused by the fact that current US law requires any gas vents or muzzle brakes to be soldered on. Most current weapons combine gas venting with a flash suppressor.

Thoughts?

Are there particular problems with the firearms RAW that you have identified, or do you just want an added layer of realism? If its the later, than I say you do whatever floats your boat. If you are trying to address game mechanics, then you need to be more careful about balance.

Given that:
- The extended mag rule seems totally reasonable, although a 50 rnd mag in a pistol would get a little silly.
- I'd say that -2 AP for an SMG is a little much, since ARs generally only have -1.
- Do you see the range difference making a great difference in game (i.e. enough to warrant more complex rules)?
- You are correct about the interchangeable ammo. In my old group we allowed them to be interchanged. The thing you need to be careful about is players who will then argue that an AR should do LMG damage or an SMG should do HP damage, etc. This breaks the game balance pretty quick. You have to remember that the DVs are abstract and take into account things like the accuracy of the weapon at range and the weapons utility in certain roles, etc.
- You do mean +5 dice to detect the rifle? This also seems reasonable if you want the complexity.
- Do you run into a lot of situations where you need to remove gas vents? Exchange for sound suppressor perhaps? If its a problem, I don't think having removable GVs would unbalance things.

Edit: I think another thing to keep in mind is that the abstract rules don't really have the "resolution" to account for finite things that make a measurable difference in RL (like the trend toward higher penetration in SMG ammo, for example). Things generally have to make a big difference to change the rules.

I like your extended capacity rule for clip guns. I'm not so sure that 50 is a good idea, but a slight increase would be cool. And yes, the Gas Vent rule has always made me confused. They should just have the end of the barrel threaded, or a locking mechanism like Bayonets on rifles.

Bigger Mags for Pistols have been done in RL
Artillery Luger
http://www.securityarms.com/20010315/galle...es/0900/999.htm
http://en.wikipedia.org/wiki/Luger_pistol

WMS

IMHO if you add the butt stock and that drum of ammo as shown in the pic, the pistol has just become a SA submachinegun....why not just use an SMG?

Agreed just showing how some extended magazine could look like. IIRC the snail drum magazine functioned/worked on all types of Luger, with and without extended barrel and attachable butt stock. Yes with just the snail drum, the balance would take some time for adjusting to the balance.

IIRC there was a link posted in one of the threads that showed a pistol using a type of snail drum magazine but it curled upward towards the trigger. It was a "Custom" pistol too.

WMS

Gas vents are available as accessories, which are not permanently installed. SR3 rules made them permanent, but SR4 doesn't.

EDIT: Actually, it's confusing. In SR4, it says that gas venting is a permanent alteration. But Arsenal adds rules for weapon mods. In Arsenal, weapon mods don't take up a mount, but can't be removed, while accessories take up a mount, but generally can be... I dunno, I think you're right. The devs were/are confused about gas vents

If I was to change the Combat Rules, I´d incorporate way higher range penalties and give out DP boni for good firing positions to compensate. The mod would depend on range category.

- The runners have to keep moving, while the guards can fortify positions. The sec guards profit more, helping them to make do without implants.

- Firing Stance gets to matter.

Right.

People come up with all kinds of strange variations for firearms. The vast majority don't add any real utility you can't get from some other standard firearm, probably at a lower price.