Does anyone have any thoughts on this? Positive or negative?
The most important thing to me is that you need to define your goals. You've mostly done that. One important piece to me is how do you plan to cook them? Are you planning on eating only the cockerels?
Cockerels mature at different rates than pullets. As they go through puberty the hormones add texture and flavor to cockerels. Texture means the older they are the tougher they can be so age at butcher has a lot to do with how you can cook them. You can turn an old mature rooster into a gourmet meal but he has to be cooked correctly. Otherwise he is probably going to be inedible.
The hormones also add flavor as they mature. Some of us like that flavor, others consider it too gamey and hate it. Pullets add texture and flavor too but much slower than cockerels.
Another factor is that we each have our own preferences for texture and flavor. If you are used to "store" chicken (Cornish X butchered at 6 to 8 weeks of age) you may not enjoy the texture or flavor of our cockerels. An additional complication is that different cockerels (even the same breed) start puberty at different ages. While one may start adding texture and flavor pretty young a sibling may be a month or more later.
You can find charts that say you can cook a cockerel a certain age a certain way. Those are a general guideline but I think you need to do some trial and error to find out what suits you the "best". We are all different.
Another thing to look for is at what rate they gain weight. If you are butchering them at 16 weeks you want one that gains the most weight at 16 weeks, not at 20 weeks. When you are selecting your breeders keep the ones you want to eat and eat the rest.
I agree, since you want to breed your own stay away from the Cornish X. It is too hard to consistently keep them alive long enough to breed. Some people on this forum that have had some success have crossed a dual purpose chicken with a Cornish X but even that is hard.
The Rangers are not quite as hard as the Cornish X. Some people have had success breeding them to each other but it is generally a good idea to watch how you feed them. Don't feed them as if you are trying to get them to gain weight quickly if you want to breed them. Rangers were bred to grow a little slower and to be able to forage for a lot of their food. Again, some people have bred them to dual purpose chickens.
You read a lot about how Cornish X or Rangers don't breed true. That is correct, they do not. They are crosses and you can get variation when you breed crosses to crosses. There can always be an exception no matter what you do with chickens but for the vast majority of cases your worse rejects from cross bred Cornish X or Rangers are still a better meat bird than a dual purpose bird. So is crossing them with a dual purpose breed. Still, without special techniques consistently keeping Cornish X alive to breeding age and beyond can be very hard. Rangers are easier but can be challenging.
Before the Cornish X took over the meat bird industry in the 1950's Delaware, New Hampshire, and certain strains of White Rock were the commercial meat birds in the US. When the Cornish X took over breeders stopped breeding those for meat so they soon became normal dual purpose chickens. There are very few breeders today that have Delaware or New Hampshire bred specifically for meat. One is mentioned above. If you can get breeding stock from them you are in a pretty good position but you need to learn how to choose which chickens to breed to maintain their quality. If you don't select your breeders wisely in a very few generations your flock will not be that different from many other flocks.
Another decent place to get starting stock is from show bird breeders. They breed for size, show birds are typically bigger than hatchery stock. But they do not breed for efficiency of putting on meat. Their concern for size is when they are ready to show more than when they are ready to butcher so feeding efficiency could be less. How well they work for you could depend a lot on how well you choose which chickens get to breed.
Welcome to the adventure of raising chickens for meat. It can be as simple as getting some birds and raising them to butcher age. It can be as complicated as you wish in learning how to feed them and breed them to get the chicken perfect for you. Good luck!
