Mark some eggs and leave them in a nesting box for a while like you started doing. You most likely will have to leave them for a long period of time and swap out fresh ones every now and then. Leaving the eggs in the nesting box won’t snap them into being broody right away and some won’t bother sitting until there are a good 14-15 eggs piled up. Your barred rock might be your best bet on going broody with being heritage breed (although my hatchery stock never did). My best broody’s aren’t from a Hatchery, but a breeder who focuses on older heritage lines. I specifically invested in these because I wanted to let the hens brood every spring to refresh the flock yearly. A lot of the hatchery stock have had the broodiness bred out of them, but not all. My hatchery welsummer, speckled Sussex and Orpington have gone broody along with my bantams, but they are all heritage breeds. Here’s a picture of my English Orpington hens (from the breeder) and one of her chicks she just hatched out this morning.
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