In smaller cases, with pronounced necks, case shape has little effect. I believe that is because the neck prevents much of the powder from moving into the barrel without being properly ignited. Long cases (over 2.5"), with minimal or no necks are a different story.
When the bore size goes up (starting at perhaps 35 cal), you can properly start to evaluate case shape. Take a case shape like the 9.3x74R, and compare it with something like the 376Steyer, or a WSM case. Or a 458Win with a Rigby based case.
In smaller calibers and shorter cases, no on has found a measurable difference without a battery of bench rest rifles that shoot averages in the .1" category. Not so in the larger bores. JMO, Dutch.
