You are right on very well explained, I know I tryed a few Lost River Bullets in 140gr they are much longer than the noslers, and seat much deeper, causing a powder, compaction and will have a big affect on velocity.
I have never seen the .30/378 but it must be something else, a truly long range thunder stick. I don't think I would be able to handle recoil and not be flinching on a 5 shot grouping let alone trying a 1000 yard 10 shot try.
It is sad to see the7mmwsm to die as it as so many better bullet choices, than the .270 I guess the history of the .270 over the years makes the .270wsm the bigger seller, as one member said if the .280 had been brought out ahead of the .,270 Jack Oconnor would have used it, and the .270 would have never made it.