I've reloaded for a few years but recently began working towards maximizing accuracy in several rifles. As part of this effort I recently rotated out all of my old and mixed 7mmRem Mag brass and bought brand new Winchester brass for it. I've weighed each casing and sorted them accordingly, and will be shooting through a chronograph.
In order to get a tight chamber fit in my Ruger M77, I partial resize instead of full-length resizing. But of course partial resizing unfired brass is pointless so...
My question is this: Should I load up some cheap bullets in the all of the new brass and once-fire it before I begin working up test loads with it? My intuition tells me that since the case volume will be slightly larger and chamber fit will be slightly tighter, that might have an effect on the best bullet/powder/powder volume combination. Is it likely that the best load with fired and partially resized brass will be different than the best load with new brass? Or will the difference be so small that the best load will rise to the top regardless, in which case loading and firing 50 rounds beforehand would be pointless.
Anybody have any experience to share concerning the difference in loads or accuracy between once-fired brass vs. new brass?