If you process a barred rock or probably any of your chickens over 6 months in age, they are most likely going to be tough. Try brining the bird over night. There are plenty of great brine recipes on the internet. Cornish crosses are great meat birds and should be processed between 6 and 7 weeks. If you wait any longer than that, they run a greater risk of broken legs (they are bred to have huge breasts) or heart attacks.
If your birds are free range, they are going to be leaner than cooped birds as they get a lot more exercise and eat less fatty items. The eggs will have bright yellow/orange yolks because of the higher protein content. As to a gamey taste, it depends on what they are eating. If they are eating a lot of weeds, yeah, I can see that. If they are eating mostly bugs and scratch, they shouldn't be gamey at all.