We raised seven roos from chick to 16-20 weeks for eating. The 16 week olds were probably in the 3 lb range when culled, but by 18 weeks, we were getting 5 lbs! These were RIR over White Leghorn crosses, and those boys really started getting big after 16 weeks. They did start crowing at about 14 weeks, but it wasn't anything annoying, not all the time or anything.
The meat was very flavorful, very tender, and lots and lots of it. We fried some, and roasted the others. It was really delicious either way. The meat eaters in the family are very disappointed that we don't have any more home raised chicken to eat till we raise another batch!
We didn't have a killing cone, and before we process anymore chickens, I want one of those. It would make it so much easier! We tried the broomstick method of killing and the cutting the jugular, and we preferred the jugular one, because they bleed out much more completely.
My husband helped with processing the first couple, but due to a broken vertebrae, wasn't able to help with the others. My dd12 helped process the rest. We're slow, so it took us about an hour per bird, but we did find that if you put a squirt of hand-dishwashing soap in the hot water you dip them in to loosen the feathers, it loosens them much better than without the soap.
I never thought I could "do the deed" myself, but when it came down to it, since we'd raised these from the beginning as food, and I knew I was putting healthy food on the table for my family, I was able to do it without really thinking about it. It wasn't pleasant, but I just did it, and once they were dead, from there it was just "food prep." And I've always been queasy about that sort of thing. Knowing how factory raised chickens are raised and not wanting to support that or feed that to my family made it much easier to take care of it myself.
Good luck with them. I'm sure you'll enjoy the fruits of your labors!