Projectile Weapons & Sci-Fi

[Agent 333]

Railguns, coilguns, and good ol' fashioned chemical propellant... no matter what's throwing the projectiles, there's still a hunk o' metal being chucked at an enemy. Assuming that different projectile payloads would just add qualities or the like to the damage instead of outright supplanting it, how far should this be taken?
SC2.0 has pages and pages of firearms... and (set in the near future) Shadowrun has books full of them.
The question becomes, how different can different sets of weapons really be? Do we need 30 different types of rifle? Or can I get away with, say, 5? Off the top of my head, I'd want different stats for Railguns, Coilguns, Chemical Projectile Guns, and a couple different energy weapons. Though honestly I could get away with lumping Rail and Coil guns together.
I'm inclined to come up with a strict set of rules for converting a rifle to a pistol, and/or to a HMG equivilent. Should it be more played by ear? In theory, a Rail or Coil gun will get a lot more juice out of a longer barrel than a chemical gun, though I'm not sure how much (something tells me complex math would be required to find out).
I think that I'd make "Projectile Firing" a quality that lets weapons use alternative ammo types, but also requires expenditure of resources on said ammo, making them more flexible but less economical than energy weapons.

[Agent 333]

Here's a sample table I threw together...

Code:

Name Damage Threat Range Qualities SZ/Hand
Pistols
Railgun 1d8 19-20 90ft x 5 AP 4, Ammo D/1h
Coilgun 2d4 19-20 60ft x 5 AP 2, Ammo D/1h
Powdergun 1d6+2 20 30ft x 5 Ammo D/1h
Lasgun 1d12 20 40ft x 5 AP 3 D/1h
Plasgun 2d6 18-20 20ft x 5 AP 4, unreliable, inaccurate D/1h

Rifles
Rail Rifle 2d8 18-20 90ft x 10 AP 5, Ammo S/2h
Coil Rifle 4d4 18-20 60ft x 10 AP 3, Ammo S/2h
Powder Rifle 2d6+2 19-20 30ft x 10 Ammo S/2h
Laser Rifle 1d12+2 19-20 40ft x 10 AP 4 S/2h
Plasma Rifle 3d6 17-20 20ft x 10 AP 5, unreliable, inaccurate S/2h

Heavy Weapons
Railcannon 3d8 19-20 90ft x 10 AP 5, Ammo M/2h
Chaingun 6d4 19-20 60ft x 10 AP 3, Ammo M/2h
Minigun 3d6+2 20 30ft x 10 Ammo M/2h
Lascannon 2d6+4 20 40ft x 10 AP 4 M/2h
Plasma Cannon 4d6 18-20 20ft x 10 AP 5, unreliable, inaccurate M/2h


Ammunition Damage Qualities
Standard As Weapon -
Armor Piercing As Weapon AP 2
High Explosive As Weapon + 2 Spread
Hull Safe As Weapon AP -4
Anti-Infantry As Weapon Bleed, Spread
Flaming As Weapon fire -
Shocking As Weapon electric -
Freezing As Weapon cold -

[Black Cheese]

You can do it more easily than that. Make each different weapon type an upgrade to an existing type. That is, make railgun a tag that can be added to any firearm. Then make 'em do different whatever you want them to do different.

But that last part's the key. If you just say to your players, "It's a sci-fi game. All the guns are blasters; they have the same stats but go 'pew pew' instead of 'bang'," I'm pretty sure no panties will bunch.

Ranged implements for killing people. If there's nothing particularly special about them, just make 'em line nowadays guns and be done.