Gene, "There is a need for someone to design a shoulder bump measurement tool."
Yeah. My best tool is from RCBS, it's their "Precision Case Mic". I also have the Stoney Point/Hornady tool and another one like Sinclair sells, but I like the Mic best because I get the most repeatable results with it.
The Mic has two top thimbles which screw onto the base unit. One thimble measures the case shoulder and the other measure the loaded bullets at the bore diameter of the ogive. I find the Mic really useful for this work.
The Mic also inludes a "free-bore" tool that is supposed to let us measure the length from the bolt face to the origin of the rifling. I suspect it would work pretty good with controlled feed actions but not for my push feed actions. So, I don't use that thing. I use a wood dowel for a bore rod and the bullet I want to load instead. Together, they show me the maximum load length quite well and it's done with simple "free" tools!