[Crash_00]

You get back the slots they took up (zero each since they were included already) and that's it. There's also no option to buy the gun without the stock mods, so you have to buy it then have the stock mods removed (paying an armorer or doing it yourself if you have the skills). Its also worth noting, that removing mods doesn't impact the firearms legality, so taking a silencer or grenade launcher off of a weapon will not make it restricted. (Although not all weapons with Silencers, Sound Suppressors and Grenade launchers are illegal)

[Tsuzua]

Arsenal (pg.  29)

MACHINE GUNS AND CANNONS
All machine guns and assault cannons can be equipped with
top-, barrel-, and underbarrel-mounted accessories, unless otherwise
noted. They cannot use silencers or sound suppressors and
suffer from double recoil modifiers (see Recoil, p. 152, SR4A).
Firing these weapons requires the Heavy Weapons skill.

So no silenced Guass Rifles or suppressed MGs.
Of course you can always take a barrett, slap a large Firing Mod: Full-Auto on it, pop Electronic Firing in it and a Sound Supressor, Shock Pad, and Gyro Stabilization Harness on it for a nice anti-armored troll weapon.

It's good that it's there somewhere. 

[Thermo]

Sounds kinda like the sniper rifle that Sarah Connor puts into full auto during the assault on the computer guy's house in Terminator 2.. only much, much bigger

[JustADude]

Sounds kinda like the sniper rifle that Sarah Connor puts into full auto during the assault on the computer guy's house in Terminator 2.. only much, much bigger

Actually, a Sniper Rifle going Full Auto is basically a HMG with a Barrel Extension, and inexplicably better damage. 

[TheWanderingJewels]

I seem to remember it being a four round bust mod. I was thinking perhaps High-Velocity Rounds for the ammo. AP rounds if you feel like being nasty

[Teyl_Iliar]

Arsenal (pg.  29)

MACHINE GUNS AND CANNONS
All machine guns and assault cannons can be equipped with
top-, barrel-, and underbarrel-mounted accessories, unless otherwise
noted. They cannot use silencers or sound suppressors and
suffer from double recoil modifiers (see Recoil, p. 152, SR4A).
Firing these weapons requires the Heavy Weapons skill.

So no silenced Guass Rifles or suppressed MGs.
Of course you can always take a barrett, slap a large Firing Mod: Full-Auto on it, pop Electronic Firing in it and a Sound Supressor, Shock Pad, and Gyro Stabilization Harness on it for a nice anti-armored troll weapon.

hey guys, don't mean to be a rules whore here, BUT.... if you're playing by 4th ed rules the entry on page 152 reads as follows.,

  Any weapon classified as a Heavy weapon (light, medium, and heavy machine guns and all assault cannons) has all it's uncompensated  recoil doubled. For example if a medium machince gun fires a 6 round burst it only has 3 points of recoil compensation (reduceing it's recoil modifier from -5 to -2), it's final modifier would be -4 (-2x2=-4). Any Shotgun fired in burst mode also doubles the modifier for any uncompensated recoil.

The uncompensated part is the most important bit in there. which means it's not all the recoil from base, it's only the uncompensated stuff that's doubled up. which makes a HUGE difference. (I spent 2.5 hours trying to cram the most recoil comp I could into a panther XXL so that It could fire full auto, but still not suffer recoil modification. My GM pointed that rule out to me and saved me plenty of frustration.)

Sounds kinda like the sniper rifle that Sarah Connor puts into full auto during the assault on the computer guy's house in Terminator 2.. only much, much bigger

That actually wasn't a sniper rifle. It was an M16A2 with a laser sight barrel attachment and a scope mounted over the iron sights held in place by a screw mount, modified for SA and FA. I say this because the magazines used in the weapon seen during that scene were made to fit 5.56x45mm rounds. It is true that Back in 1996 there was a DMR, verison of the AR-15/M16 design, but it was chambered in 7.62x51 and wasn't widely used. (to my knowledge.) much less capable of FA selection. Gun freak/

[Stry]

Sounds kinda like the sniper rifle that Sarah Connor puts into full auto during the assault on the computer guy's house in Terminator 2.. only much, much bigger

She uses a M4 with scope, laser sight and sound suppressor.   In theory it is already in the game.  Personally I seriously doubt any one would ever make a burst fire or full automatic sniper rifle recoil would be far to much on any seriously aimed shot.  If you want an automatic sniper rifle just use a battle rifle.
 

[JustADude]

If you want an automatic sniper rifle just use a battle rifle.

Actually, given the heavy calibers they fire at, a full-auto sniper rifle would probably be more accurately portrayed as a HMG with an extended barrel and a scope.

The game borks it up by giving the "light" sniper rifles the same damage and AP as a HMG, but the modern .50 sniper rifle fires the .50-BMG (Browning Machine Gun), the same load used by the venerable, and still unsurpassed Browning M2 "Ma Deuce" machine gun.

And, just for awesomeness, here's a declassified video showing what a real .50 sniper rifle is capable of doing: LINK

[Stry]

Technically speaking .50 rifles are not commonly considered to be "sniper rifles" they are commonly used as "anti-material rifles."   

[CanRay]

Technically speaking .50 rifles are not commonly considered to be "sniper rifles" they are commonly used as "anti-material rifles."

Also called, "HOLYSONOFAMOTHER****ER!!!" 

[Xzylvador]

They fire antimatter?!! Awesome!

[CanRay]

They fire antimatter?!! Awesome!

Anti-MATERIAL, not Anti-Matter. 

They're used to destroy military material.  Such as light vehicles, mortars, airplanes, UAVs, large groups of people mass charging, a good part of the Dictator's Palace.

[JustADude]

Technically speaking .50 rifles are not commonly considered to be "sniper rifles" they are commonly used as "anti-material rifles."

True, however the Barrett and the Minotaur rifles are both explicitly mentioned as being AM rifles, so RAW doesn't differentiate based in caliber until you get to the Assault Cannon.

[CanRay]

RAW has calibers? 

[JustADude]

RAW has calibers? 

I mean the Sniper vs AM, and you know it.

The Big Dakka, to mix realities, is a different category of weapon IRL, but the system doesn't care. It's a Sniper Rifle right up until it's big enough to be an Assault Cannon.