In Car Wars hand weapons, The Shotgun seems to be the poor cousin of Rifle. They each cost $120 and take 2 GE. In alternate encumbrance, the Shotgun only weighs 8 lbs to the Rifle's 10 lbs. The Shotgun hits on a base of 6, better than the Rifle's base of 7. That is the only real advantage a Shotgun has as written. The Shotgun also only has 10 shots compared to the 20 in the Rifle and does only 2 points per hit compared to 3 points per hit from the Rifle.
The Double Barrel Shotgun is interesting in that you can choose to fire two rounds from the 10 shot magazine at once, increasing the potential damage to 4 hits per firing action with two successful to hit rolls. But the base cost goes up to $200, GE goes to 3 and alternate encumbrance goes up to 12 lbs.
Both the Rifle and the Shotgun have a maximum range of 20" - or scaled to 100 yards. That seems a bit much for a Shotgun. Personally, I can not reliably hit anything further than 40 or 50 yards with a shotgun. I'm sure there are people who can. I am not claiming to be a master shotgunner - just an average bloke with experience in using the weapon.
In my opinion, the advantages of the shotgun are versatility and power at close range. There are other advantages and disadvantages. However, these two I feel are neglected in Car Wars. I would make some proposals to change the Shotgun to reflect those advantages and disadvantages and separate it from the Rifle.
First, I would reduce the maximum range to 10" or 50 yards. I feel that is the practical effective range of a Shotgun, especially in a combat situation.
Second, I would have the Shotgun deliver double damage at Point Blank range - 4 hits per barrel. This would reflect the effect of the increase in the number of buckshot pellets hitting the target before the load begins to spread too much.
I have also toyed with the idea of slugs for the Shotgun. Initially, I thought slugs would be CPS $5, decrease the base to hit from 6 to 8, do full damage to vehicles but would not get the double damage at Point Blank range I would propose for the regular Shotgun rounds. Slugs would also be subject to the 10" - 50 yard maximum range suggestion for normal rounds. What do you think? My concern is that for $250 (a Double Barrel Shotgun with Slugs) you almost supersede the AVR - you only have 5 shots with both barrels and have to make a separate to hit roll for each barrel, but its $400 cheaper and is lighter. I think it would be an interesting option. I worry if it disrupts game balance, though.