Jun 8, 2019, 06:29 PM
You're just having average to bad luck, I can't tell at this point (270 eggs is not a lot when masuda breeding). You're still bound by the normal shiny odds when doing masuda breeding, which can sometimes take a very long time to get a shiny. Swap-breeding does not actually improve your shiny odds in any way. The main reason people use Magikarp for swap-breeding is that it has the fastest hatch time.