Yes, but your meatier BR is going to require a lot of selective line breeding and possibly more than one cross breeding. And due those steps you may not recognize your BR anymore.
Project to purebred - Page 2
Constant and detailed management of the breed stock and a ruthless soul with regard to culling and you can get a noticeably larger version of any chicken same as making bantam versions.
I agree with Fred, but would like to add an additional thought or two.
In the science world, the term purebred can mean an animal is homozygous at a specific gene locus. You can have a bird that carries two recessive genes at a specific locus and the bird is purebred. In another bird, there can also be a pair of dominant genes at the locus and the bird is still purebred.For example, at the E locus, a bird can be purebred for extended black while another bird can be purebred for wild type at the E locus. If you cross the two previously mentioned birds then the offspring are hybrids or heterozygous.
The term purebred, as associated with chicken fanciers, indicates the bird will breed true (this is not true for genes that are incompletely dominant). If a person crosses a purebred rhode island red male with a purebred rhode island red female, the genetic makeup of the offspring should be the same as the parents (usually, but not always). If you cross a purebred female delaware with a purebred rhode island red rooster, then the offspring are hybrids: males will have a silver phenotype ( what the bird looks like) and females will have a red phenotype. The delaware and the rhode island red share some genes that are exactly alike. The columbian gene is a gene that both the rhode island red and delaware share. Even though the offspring are hybrids, they can be purebred for a certain gene and in this case they are purebred for the columbian gene.
If you mate a rooster and hen, and over 100 offspring are hatched from the crossing, and all the offspring are the same phenotype. The chance is very good that the rooster and hen are purebred. if you take the 100 chickens and put them in a big pen and let them randomly breed and over time the offspring are all the same phenotype; the original parents and all the offspring are purebred.
get a few male cornish cross and milk them ( get sperm from them) and artificially inseminate some rhode island red. The resulting F1 offspring will be larger than the rhode island red but not red. They will be white or white with buff heads, Then cross the largest male F1 offspring with his largest sisters. See what you get- a few will be red and others white.
I made the cross but with buff orpington male over cornish cross females.
Edited by Wappoke - 6/9/16 at 4:58pm