Gun turret
Gun turrets are very basic and cheap defensive structures and the simplest element of automatic defenses. They use magazines for ammunition which can be refilled manually or by inserters. They do not require power and can operate practically anywhere as long as they have sufficient ammunition. Gun turrets deal double damage per shot as compared to the man-portable pistol and submachine gun, but have somewhat lower fire rate than the latter, so absent any turret-specific upgrades it does 1.33 times as much damage per second as the submachine guns. The gun turret receives bonuses from technologies that improve bullets so it keeps pace with the submachine gun as those improve, and they also receive bonuses from their own damage upgrade. These two damage effects stack multiplicatively: fully upgraded, bullets do 2.2 times as much damage as a standard bullet, and turrets do 2.2 times as much damage as a standard turret, so bullets from a turret do 2.2×2.2=4.84 times as much damage as without the upgrades, totaling 19.36 damage from regular and 48.4 damage from piercing bullets, more than fully-upgraded laser turrets can provide, though still not quite enough to kill medium spitters in a single shot.