About 3 weeks so I know young but I've read some can sex them fairly easy and in my research I just wasn't positive. He/she is my only one but it's dominant and one of the biggest. Bought as 90% pullet rate so likely is but never know!
There is a trick to sexing young BR but i've read that most hatchery breeding stock BR have had the trick bred out of them and the trick only applies to a select few hatcheries and breeders birds. I'm not positive though, maybe someone will come in who can sex a young BR.
females generally have a dark wash over yellow legs - males have yellow legs. It's especially hard to tell in photos where a red lamp is in use. Females have distinct black barring and narrow areas of white. Males tend to have grayish barring and wide areas of white.