I have been developing loads over a chronograph for quite a long time and done so with enough same cartridges but varying rifles/tubes to have an opinion though no experience with the 270, which I realize is what you have asked.
Anyways seeing the data posted throughout the thread surprises me none and is about what I would expect. I think it is mostly a matter of chamber and bore tolerances affecting pressure. Might add any differing barrel lengths can affect results as well.
I'll also add that contrary to conventional wisdom I more often than not find custom tubes shooting same loads slower than the factory tube they replaced. I chalk that up to smoothness and consistent tolerances making for a smooth pressure curve. FWIW.
