I took the Ruger Thunderbolt last night, and rebuilt it using the Cannon Companion's FSG: here's the results:
Heavy Pistol[ruger thunderbolt]
Conceal 5 (4. 4[special])
10 Round Clip(2. 12 Rounds)
Semi-Automatic (1. BF)
9 Moderate Damage(1. 12 Serious
2.75 Kilos(1. 3.25)(3. 2.75)(4. 3.50)(5. 2.75)
Firearm Construction Units 2(1. 1)(4. .25)
Design Point Value 120(1. 220)(2. 224)(3. 234)(4. 374)(5. 389)
1. switch to BF(+95DP, -1 FCU, +.5 kilos)
2. Add 2 rounds to clip(+4 DP)
3. Lighter Alloy(+10DP -.50Kilo)
4. Apply Recoil Comp[Gas Vent III](+.75 Kilo, -.75 FCU, +140 DPV)
5. More lighter Alloys(15DP -.75 Kilo)
original frame cost = 600
Modification Costs = 1345
final price = 1945
now that looks like Ruger is being awful generous to Lone Star producing 2000 nuyen guns for them. However, lets say that since Ruger is a Large Corporation, they have access to cheaper materials, and automated factories. lets say that reduces the DPV Value by half. then your price ends up being 973 nuyen to produce, granting Ruger 27

To prove a point let's use the same assumptions for a Ares Predator III
Heavy Pistol [ ares predator III]
Conceal 5 [special conceal 4]
10 Round Clip(1. 15 Round Clip)
Semi-Automatic
9 Moderate Damage
2.75 Kilos (2. 3.0 Kilos)(3. 2.25Kilos)
Firearm Construction Units 2 (2. 1.5)
Design Point Value 120(1. 130)(2. 310)(3. 325)
1. Increase Clip(+10 DP +5 Rounds)
2. Add Smartgun Internal(+.25 Kilo, -.5 FCU, (1.5x frame cost) 180DP)
3. Weight Decrease(+15DP, -.75 Kilo)
original frame cost = 600
Modification Costs = 1025
final price = 1625
Wow! that's incredibly expensive for our good friend, and @ 650 nuyen, a runner is getting one Hell of a deal! Now if we assume that the frame costs half as much for a well maintained facility, then the smartgun also doesn't cost as much(90DP), the final price when you half the total cost of manufacture is 587.50


I haven't done any other mods, but I hope to find them all like this. I figure if you divide the cost of manufacture in half, and then multiply by 5, you arrive at the appropriate cost.
Anybody tried this or want to attempt? thoughts comments? Any help is appreciated, since I'm going to be building a gun mod/redesign program for SR3, and I need to come up with some good solutions to the "canon guns don't apply to the FCG rules."