The first two rifles I built used pre-carves from a company who is no longer in business. They both had ramrod channels routed just like yours. One needed more scraping than the other to adjust the rr channel for a smooth fit, but they both finished into fine looking, functional rifles. At that time, I assumed all pre-carves where made that way. I know routing is not the traditional method, but you will be the only one who knows. For my present project, I bought a pre-carve from a vendor whose work gets high marks from members of this board and the rr channel was bored its full length. I paid a lot more for it, but the precision work will save me a lot of time. I know your stock does not meet your expectation, and I don't know what you paid for it, but based on my experience and your photos, it should be usable with some extra work.