Production reds aren't a mix,well not all.
I have done a lot of research and the only possible thing in a Tractor Supply hatchery,a production Red would be likely bred with Red Jungle fowl.
The Production Red is bred of RIRXNewHampshire(The "Proper" way to say the breed)X(Sometimes,often) Leghorn to make the PR's egg production 100% better.
After having the Production Red with every flock,they lay well,an d surprisingly can't be sexed at age.
Great egg layers laying X large eggs,although I've never got a "Double" yolker from my 3 or 4 PR hens.
as for the Red sexlink,nah,never gettin' another 1.too bossy and aggressive,and from my experience,small eggs,horrible layers.:/
I am not arguing...I have very little experience. But I have had a Red sex link for about 3-4 months now. She is the best layer...an egg every day. She is friendly and curious....not bossy at all. She is on the lower end of the pecking order. I want more like her. Had several double yolkers and huge eggs while she was adjusting to laying. I hope there are more like her and she is not a fluke.