My very first layer was a black sex link, sadly she disappeared a few weeks ago, and she started laying at 21 weeks. I have heard some start as soon as 18 weeks. She laid a nice medium brown egg and eventually they get to be large size and a nice brown.
Definitely a Black Sex Link (Black Star) pullet. I've raised them for years and mine have usually started laying from 20-24 weeks (sometimes a little earlier and on rare occasions a little later). Once they start laying, they are egg laying machines, commonly churning out more than 300 eggs per hen per year. )
I'm getting some since that there is some confusion between on some of the posts between Black Star and Black Sex Link. Black Star is one label under which some hatcheries (Murray McMurray for example) market their Black Sex Links. Another label under which Black Sex Links are sometimes marketed is Bovans Nera, but no matter which label Black Sex Links are marketed under (Black Star, Bovans Nera, etc.), they are the same bird. Black Sex Links are hybrids produced by crossing a red gene rooster (usually a RIR) with a barred gene hen (usually a BR). The resulting offspring can be sexed by color at hatching (male chicks are black with a white spot on the tops of their heads, and female chicks are solid black). As they mature, BSL roosters resemble Barred Rock rooster and BSL hens are black with some reddish or copper colored feathers around the neck area. No matter what label they are marketed under, Black Sex Links are egg laying machines. outlaying either parent breed. It's one of the interesting quirks of hybridization. I've raised Black Sex Links for years (along with dozens of other breeds and hybrids), and they have been my best layers, commonly churning out more than 300 eggs per hen per year.