I'll try and resolve this by comparing existing weapons with the proposed reduction of gauss cannon to approximately 1/6th of their current size.
I will use 8000 RP as the max tech level for this. All the systems below will use the following fire control for missile defence, which is a standard 4x Speed system.
Fire Control
50% Accuracy at Range: 32,000 km Tracking Speed: 16000 km/s
Size: 4 HS HTK: 1 Cost: 77 Crew: 20
Full size GC without turret
Damage Output 1 Rate of Fire: 3 shots every 5 seconds Range Modifier: 3
Max Range 30,000 km Size: 6 HTK: 2
Max GC in a triple turret
Damage Output 1x9 Rate of Fire: 5 seconds Range Modifier: 3
Max Range 30,000 km Turret Size: 24 Armour: 0 Turret HTK: 6
Maximum Tracking Speed: 16000km/s
Min Size GC with 8% modifier to hit
Damage Output 1 Rate of Fire: 3 shots every 5 seconds Range Modifier: 3
Max Range 30,000 km Size: 0.5 HTK: 0
This weapon has a penalty to accuracy. Chance to hit is multiplied by 0.08
Min GC in a triple turret
Damage Output 1x9 Rate of Fire: 5 seconds Range Modifier: 3
Max Range 30,000 km Turret Size: 2 Armour: 0 Turret HTK: 0
Maximum Tracking Speed: 16000km/s
Lets assume an incoming wave of missiles with a speed of 20,000 km/s. The turret tracking speed and fire control tracking speed are both the same at 16,000 km/s. The Fire control has an 84% chance to hit at 10,000 km/s and the final chance to hit is Chance to hit x (Tracking Speed / MissileSpeed), which is 67.2%. For the small GC turret the chance to hit will be 67.2 x 0.08, which is 5.4%. However, you can fit eight small turrets in the same space as one large one so the real comparison is nine shots at 67.2% vs seventy-two shots at 5.4%
Lets compare this to a 10cm laser turret of similar size and a non-turreted 10cm railgun, both of which are popular anti-missile systems. Both these systems also need power plants so those will have to be taken into account as well within the 24HS.
Twin 10cm C3 Ultraviolet Laser Turret
Damage Output 3x2 Rate of Fire: 5 seconds Range Modifier: 4
Max Range 120,000 km Turret Size: 8 Armour: 0 Turret HTK: 2
Power Requirement: 6 Power Recharge per 5 Secs: 6
Maximum Tracking Speed: 16000km/s
A pair of twin 10cm Ultraviolet lasers plus power planets is 20 HS. If we assume a twin and a triple, it actually works out to 25HS but that is close enough. That setup allows for five shots at 67.2%, compared to the nine of the equivalent GC. Although that makes the GC almost twice as good, that is acceptable because the laser can also be used in an anti-ship mode. The anti-ship capability of the laser vs GC even at point blank range is 15 vs 9 and the laser has a longer range as well.
10cm Railgun V4/C3
Damage Per Shot (4): 1 Rate of Fire: 5 seconds Range Modifier: 4
Max Range 40,000 km Railgun Size: 3 HS Railgun HTK: 1
Power Requirement: 3 Power Recharge per 5 Secs: 3
Now the railgun tracking speed is limited to the speed of the ship. Lets assume 4000 km/s for an Ion-engine escort. The chance to hit is therefore only about 16.8% (84% fire control x 4000 ship / 20,000 missile) but the railgun gets four shots. Each railgun is only 3 HS so allowing for enough power plants (2/3HS per railgun), that gives us approximately 6 railguns with 24 shots at 16.2%. The railguns are reasonable at point blank range against ships as they have a higher potential damage output than the lasers but only against slower targets
So that gives us an anti-missile comparison:
Large GC: Nine shots at 67% (Estimated Missiles Destroyed: 6)
Lasers: Five shots at 67% (Estimated Missiles Destroyed: 3)
Railguns: Twenty-four shots at 17% (Estimated Missiles Destroyed: 4)
Small GC: Seventy-two shots at 5.4% (Estimated Missiles Destroyed: 4)
Lets also assume an anti-ship role vs a 4000 km/s target at point blank range
Large GC: Nine 1 point shots at 84% (estimated damage 7.6)
Lasers: Five 3 point shots at 84% (estimated damage 12.6)
Railguns: Twenty-four 1 point shots at 84% (estimated damage 20.1)
Small GC: Seventy-two 1 point shots at 6.7% (estimated damage 4.8)
The railguns look good in anti-ship mode but they have a max range of 40k and the GC have a max range of 30k. The laser can shoot out to 120,000 km.
Now lets make the GC one-sixth the size and run the numbers again.
Anti-missile comparison:
Large GC: Fifty-four shots at 67% (Estimated Missiles Destroyed: 36)
Lasers: Five shots at 67% (Estimated Missiles Destroyed: 3)
Railguns: Twenty-four shots at 17% (Estimated Missiles Destroyed: 4)
Small GC: Four hundred and thirty-two shots at 5.4% (Estimated Missiles Destroyed: 23)
Lets also assume an anti-ship role vs a 4000 km/s target at point blank range
Large GC: Fifty-four 1 point shots at 84% (estimated damage 45)
Lasers: Five 3 point shots at 84% (estimated damage 12.6)
Railguns: Twenty-four 1 point shots at 84% (estimated damage 20.1)
Small GC: Four hundred and thirty--two 1 point shots at 6.7% (estimated damage 29)
Now it may just be me, but that makes gauss cannon amazingly, game-breakingly good. A single escort is going to be mowing missiles down in hundreds, not to mention completely obliterating anything that appears through a jump point. Here is a 7500 ton escort with eighteen triple GC turrets that are 4HS each instead of 24HS. It can put out one hundred and sixty-two shots every 5 seconds with a 100% modifier to hit. That means assuming 20,000 km/s missiles, it will kill more than one hundred missiles every 5 seconds! If used as a jump point picket ship, it could inflict 136 points of damage every 5 seconds vs a transiting ship moving at 4000 km/s. Bearing in mind that it takes 30 seconds or do to recover from transit, this ship is going to able to inflict 1000 points of damage before anyone could respond.
Tennessee class Cruiser 7500 tons 1675 Crew 3180.4 BP TCS 150 TH 600 EM 0
4000 km/s Armour 1-34 Shields 0-0 Sensors 1/1/0/0 Damage Control Rating 4 PPV 72
Annual Failure Rate: 112% IFR: 1.6% Maintenance Capacity 1060 MSP Max Repair 138 MSP
Ion Engine (10) Power 60 Fuel Use 70% Signature 60 Armour 0 Exp 5%
Fuel Capacity 150,000 Litres Range 51.4 billion km (148 days at full power)
Triple GC R3-100 Turret (18x9) Range 30,000km TS: 16000 km/s Power 0-0 RM 3 ROF 5 1 1 1 0 0 0 0 0 0 0
Fire Control (3) Max Range: 64,000 km TS: 16000 km/s 84 69 53 38 22 6 0 0 0 0
Active Search Sensor (1) GPS 21 Range 210k km Resolution 1
Now I don't mind if players want to change the stats of weapons within Aurora, it is that type of game after all, but based on the above I just cannot see any way I could drastically reduce the size of gauss cannon. I went through a similar exercise when I created them, which is why they are the size they are now.
Steve