Kathy...my BRs that I hatched from Kraig Shafer's stock are looking a lot like your Horstman birds. I found out that the people that are REALLY into rocks have bred for a "slow feathering gene" in the BRs (Jamie, ie Ducktang's, will have it too). This gene (for whatever reason) will cause the barring to be perfectly perpendicular to the shaft....perfect parallel bars of white and black. Those without this gene they tend to have a "V" shape to the feather coloring, I never noticed it before, but my BRs from Lockehearts have the "V" shape to the black and white color on the feathers.
I just hatched some BRs from Tom Wheeler and he told me to expect the same. I have some 8 week olds in my grow up pen that have a thin strip running right down their backs that have nothing but "down" still there.
I noticed that my Columbian Rocks have a similar feathering trait (slow) but I have yet to find out what or why this is in that color pattern.
Looks like my last hatch of BBS rocks produced me 2 blue pullets, 1 blue roo and 1 blue barred roo. I am planning to keep the 3 solid blues, but the blue barred will be going as he will throw barred offspring.
I also just hatched some White Rocks from SQ lines. Was told to expect birds larger than I had seen before in Rocks....but that these would be an example of what "rocks should be". I am planning to use them to improve the size, type and leg color of both my blues and my columbians.
Hope everyone is well.....it's storming here! Have a great Memorial Day everyone and remember all those who have and are serving on our behalf in the name of freedom!!