Good point BX....especially when you take into account that Galactica herself only has what, 24 of these turrets?
But there's another thought here: Galactica had to dedicate a lot of internal space for the Vipers, for the hangars, for the Vipers ammo and fuel....
Space that the Cygnus, because it only carries a few Raptors, can use for more guns...
Still, Cygnus IS a bit overgunned....but maybe the turrets have a different caliber than those of Galactica?
Like a cruiser in WWII had smaller guns than a battleship, but sometimes more of them....? (they would have a higher rate of fire also....)