I have an enclosed outer pen with a small house (old dog house) in it, that the chickens can go out into via a door with a ramp from inside the hen house. I sometimes close this off from the main coop, and use it for new moms and chicks for a few days, to let the chicks get off to a good start, or as a baby pen for chicks out of the brooder, but not big enough to let free-range yet. There's a door that opens onto the fields from that pen, plus a larger run on the backside of the coop, with another door to the greater outdoors, plus the main front door to the coop. In the daytime, all the doors are open, so all the adult birds and feathered-out youngsters can go out to roam free if they want. All of them do, except when I have Cornish X's. They prefer to stay in and eat. (Yes, I do understand that this is what they are bred to do.)
When I've raised Cornish X's, I was pleased with them when they arrived. By the time they started to feather out, they just seemed like poop machines. I was mucking out the coop every few days, mostly because they don't go outside much. They don't want get away from the feeder. They eat a lot more than other chickens, and so they poop a lot as well.
The first batch, I lost a few that dropped dead from getting fat too fast, and a lot got to where they couldn't walk. The last batch, we had a killer heat wave, temps over 100 for several days in a row, and I lost several to the heat. My regular flock handled the heat without a problem, but they would go up to shady areas where it was cooler. The X's won't do that. They had shade and plenty of water, but they still didn't tolerate the heat well, and the coop's just not as cool as it is out on the grass, under the shade trees.
After the first batch, I talked to somebody on staff at Murray McMurray, and she recommended taking the food away in the evening, hanging the feeders so they have to stand to eat, rather than lying down or resting on their keels, and told me what to do if one of them stuffed himself into insensibility anyway. (isolate the bird with no food, but plenty of water, make sure he can stick his beak in it where he's lying down. If he doesn't start drinking on his own, you can drip some in his beak to get him started. I didn't have to do this, but am just passing along what she told me.)
So I did it they way she said, and the next batch did a lot better. By the time they were 8 weeks old, they were still walking, but even so, looked like it was getting difficult. I also had started taking them outside the coop in the afternoons, I'd carry them out onto the grass a ways out from the coop, so they'd get a little green stuff to eat, and have to get up and walk just that little bit back to the coop. That seems to help a bit too, with the overall condition of the birds. And give a me a chance to clean the coop while they were outside.
By the time they reached 8 weeks, I was ready to do them in, I was just sick of cleaning after them, (the stench is awful) and they just don't act like normal chickens. There's something zombie-like about them. They're sort of like feathered slugs.
I've only raised a few batches of these, but I don't think I want to raise them anymore. I want to try some of the color rangers. I know they don't get as big. They also don't stay inside pooping constantly, according to what I've read from people raising them, so not cleaning up after them as much as the C-X's would be a big plus for me.
I have a laying flock, made up of various dual-purpose birds. We eat the extra roos. No, they aren't fryers. No, they aren't as big. Yes, they do taste very good, and when prepared and cooked properly, they're nice and tender. You can't just cut them up and fry them, they're too tough. I crock pot or pressure can, and use the meat in all kinds of dishes, and the broth is wonderful. Yes, I do understand the difference between them and the meat breeds.
What I want to do is try crossing purebred Cornish roo (yes, I know the difference between purebred Cornish and the meat breeds) over various breeds of dual-purpose hens, to see what makes an acceptable table bird for my own tastes. One of the reasons I want to do this is so that I can maintain a sustainable flock of meat producing birds, without being dependent on buying hatchery chicks every time I want meat birds. I can't do that with the C-X's. This would also give me the flexibility of hatching out smaller numbers at any one time, so I could raise and process a dozen at a time (or thereabouts) and not have such heavy processing days when it's time to butcher. Over time, with some luck, perhaps I'll have a bird of cross-breed origins that can breed true and be a sustainable meatish breed, even though they will not be as big as the Cornish X's.
An acceptable table bird, for me, would dress out to around 3 1/2 to 5 lbs by the age of 12-14 weeks, and be tender enough at 10 weeks to fry, (even if it was a little chewier than the X's, that's ok) tender enough at 14 weeks to roast. Healthy enough that if I wanted to keep some of the hens and a roo for further breeding experiments, they wouldn't drop dead from CHF. They'd be fairly active and like to run around and forage in the pasture.
There are a couple of individuals that, for some reason, take great issue with me or others, for choosing to try this, and seem to find the whole idea an affront to them, personally. It isn't. It's just my choice, for myself.
Sustainability is important to me. I want to know that if something weird happened, and we couldn't get the hatchery meat chicks, I'd still be eating chicken, even if it's all crock pot birds. That's not a concern for some, and I understand that. I don't care if others choose to raise X's or any other kind of bird, that's their choice, and none of my business.
For those who like the X's, and have done well with them, great. I'm happy that you have birds you're pleased with. I'm happy to see people raising their own meat, regardless of what breed they choose.