Interesting questing. One I cannot readily help with.
I got thinking though. The Quickload intrinsic data for bullets is sometimes very rough.
Gerard Schulz of GS Custom, South Africa, for example, is slowly retesting each bullet and adding new data.
It might just be that rough bullet data may outweigh any barrelspecific crosssections.
Example:
I cannot get accurate QL prediction with Barnes TSX bullets.
I have proven load data.
Lab-tested the loads for actual pressure.
Chronographed the loads.
With Hornady Cup and Cores FN it works perfectly.
QL is a useful tool, but needs refinement regularly I guess.
I will play a bit with the bore crosssection on that example above. Let you know if anything interesting comes up.