I had noticed that they looked very similar to my Rhode Island Reds, and assumed they were somehow related. Just didn't have any idea what else they did. Any idea what will happen when they mix with my Australorp Roos?
Australorp (black? as is typical) rooster bred over red sex links will get you "mutts" that lay brown eggs well and likely colored black, both genders.
If your rooster is white, likely all chicks will be mostly white with red bleed through.
If your rooster is blue, you will get black 50% and blue 50% both genders.
You can never breed a Gold/Red/Comet sex link to anything (not even another RSL/GSL) and get anything other than a mutt as sex linking only works the first generation to produce a hybrid. It is actually due to the color genetics that lay on the genetic strands (the Z, or long strand) that produces the sexable traits at hatch. It uses a red (roo) over a silver (non dominant white) hen (silver is dominant over red...roos are ZZ while hens are ZW...the hen then determines the sex and the color as her Z carries silver.) This produces"white" roosters with red bleed through and red hens with white bleed through. Breed that progeny again, and it is simply mixed genetics bred to something else with no gender difference in color.
Breeding to black will produce mostly black chicks, with possible red bleed through, as black is dominant over red and silver.
RSL/GSL tend to be heavy egg producers (with often ovarian cancer or other issues by year 2). Australorp are also very good egg producers but without the health problems of the RSL/GSL. Both lay brown eggs, so you will get shades of brown...and plenty of them. Both are fairly docile birds, with the Australorp being a bit heavier, so you'll get a mid-weight between them that should be fairly docile.
So it is a good breeding for getting solid, sustainable, egg layers. Keep doing that, and you'll eventually even out the production, body and temperament to have healthy laying hens. Only breed from your best in health and temperament thereby weeding out undesirable traits.
LofMc