While porcupine might have a lower range the kismet laser, privateer gun turret and mothership gun turrets have roughly the same - but to meassure this correctly you have to make a team with quad pilot and privaterrs/mothership gunner and mark each other with teamtarget.
You will notice that the main disadvantage for privateers and motherships doesnt come from a lower shooting range of the gun but from the fact that the ship desginers didnt take into consideration the size of the privaterrs and motherships which allows quads to have a lower distance to the privateer/mothership body then to the respective gun turrets.
This is what creates blindspots in certain areas and advantage ranges in others. However usually the larger ships cant put the range advantage in certain areas to use since quads can maneuver much better and therefor always keep close to the blindspots.
Kim stated in an interview severl months ago that they were looking into fixing the current gunning range issues, here is hope that this might happen on the next major space update.
For motherships i have provided an detailed overview of gun turret assignments and their range differences via support case to mindark around half a year ago, for privateers i guess someone might still need to do it.
But in general in my opinion gun turrets should have much longer shooting range then weapons of smaller spacecrafts - this could be balanced out by slowing down tracking speed of the turrets and indirectly forcing quads into closerange combat to gain speed advantage to dodge fire instead of sitting at the border of shooting range diving in and out which has nothing to do with an interesting spacefight neither in any scifi movie nor in computergames.
*small derail:
Exspecially in regards to motherships i think a size adjustment to make them equal in displayed size to the ringtorne mothership down on calypso would add also alot more options for a versatile and interesting spacefight scenario as fighters really would gain opportunities in close combat that way while motherships larger gunning range would be a must - this would also allow for more space on the hangar deck to spawn shuttles next to each other instead of stacking them into each other.
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