[moineaux]

Does anyone know what the results would be if I hatched eggs of a Black Rock fertilised by a Light Sussex cock?

[bantam novice]

No idea but I would love to see the chicks 

[Casey76]

You'd get a mix and match from traits of all parent stock (RIR, BPR and LS)   But they wouldn't be sex-linked

[moineaux]

Apparently crossing hybrids doesn't always produce viable offspring but I wonder if this is the case with a pure breed and a hybrid? I have a very handsome LS cock and a BR that has laid an egg every day since November last year so I'm hoping for stunning results! Only one way to find out...

[Spana]

I've had Black Rocks x Light Sussex, also BR xDorkings.  Ive looked through my photos but can only find the Dorking x.  I can show you that if you want, they looked very similar to me but i suppose an expert would see the differences.

They were all nice biggish hens but neither X laid as well as the true BR.

[Casey76]

Apparently crossing hybrids doesn't always produce viable offspring

Well if this was true for chickens then we wouldn't see so many "farmyard mixes!"

Even if you cross F1 to F1 you will get viable offspring, they just won't look like the parent stock, but a mix of traits from the "grandparents"

Black Rocks (Rhode Island Red x Barred Plymouth Rock) are already bred for high productivity.  If you cross that back to a LS, you will probably get a slighly heavier bird, and a slightly lower egg production, and a higher chance of pullets going broody.

[Spana]

you will probably get a slighly heavier bird, and a slightly lower egg production, and a higher chance of pullets going broody.

Thats sums it up nicely Thats just how they were 

On the plus side they cost nothing other than rearing costs and we had the cockerels for dinner.