I would go with pullet too.speckledhen: I can sex all BR chicks at hatch with relative certainty. I've written this list so many times, but here goes:
Males: larger, splotchy headspot, lighter silvery/grayish color rather than black, no or little black down leg fronts
Females: headspot is more defined and smaller, down is very black, legs usually have dark wash down the front.
These, taken together, will give you the sex about 90% of the time. The other 10% aren't as clear and can fool you.