Thanks - It turns out it was not the cases or the dimensions -
it was my brain not fully engaging! It was driving me nuts! Ultimately - I may not need the step to run the cases back through my new/used 375 H&H die to reset dimensions in the cartridge!
Story Follows: I had made two cases from 358 Norma magnum brass. The bolt would not even think about closing on, and both were "really close" to the chamber cast dimensions as well as the dimensions in Donnelly. One was "at" the shoulder length from the 35 Ackley die (same dimension - 2.05"), the other was pushed down far enough to get away from any shoulder/taper dimension problems. So I figured I had abused the cases enough that running them through a 375 H&H Magnum Die (without the expander) ought to sort out any dimensional indignities and allow me to sort of start over. Dies came in over the weekend and I did that this evening. All I really needed to do after that was trim cartridge length a few thou, and EVERYTHING was now at or below the numbers I had for the chamber!!
Still -
ZERO Interest in the bolt closing. OUCH!!. Resisted the temptation to quit, get an adult beverage and watch sports for the rest of the evening and then put my engineer brain to work on it. I had taken a M1903 drill rifle completely apart for another project two years ago, like 99.9% apart. Great Fun - learned a lot!!. That meant I knew how all the pieces fit and worked together.
Step by step I went through the process of what could possibly be happening. Obstructions, misreading the micrometer, misreading the dimension diagrams, missing pieces, etc., no, no and NO. Finally -
and I am apparently an idiot - realized it was the extractor that was not going over the rim and was just sitting there! No wonder it would not close!!
Took the two cases I had and placed them lovingly inside the extractor claw, and the one that was pushed down closed without any issue or annoyance. The one that is "at" the dimensions closed just fine with a little extra pressure the last little bit on the handle
I AM VERY HAPPY!
Now to create a third cartridge with what I think is the right process (with notes!), then a bit of fire-forming, and maybe - just maybe - make it happen!