Tangential to the main point: one hypothesis for why the artillery gunner thought that “General relativity gives you the wrong answer”, is that maybe he had an experience with a software which could either run “Newtonian mode” or “GR mode”, and the software had to make approximations for the relativistic calculation to be roughly tractable (which might be nonetheless useful for roughly solving problems where relativistic effects matter, but would only reduce accuracy for non-relativistic situations).
Now, the “GR mode” (with approximations) would be a different model from real General Relativity, but could have given the gunner the impression that GR gives substantially different (and worse) answers from Newtonian mechanics in non-relativistic situations
Tangential to the main point: one hypothesis for why the artillery gunner thought that “General relativity gives you the wrong answer”, is that maybe he had an experience with a software which could either run “Newtonian mode” or “GR mode”, and the software had to make approximations for the relativistic calculation to be roughly tractable (which might be nonetheless useful for roughly solving problems where relativistic effects matter, but would only reduce accuracy for non-relativistic situations).
Now, the “GR mode” (with approximations) would be a different model from real General Relativity, but could have given the gunner the impression that GR gives substantially different (and worse) answers from Newtonian mechanics in non-relativistic situations