Yes, after sectioning several SAME brand different batch # cases, the difference was in web thickness/case wall thickness that changed the internal capacity.
I have older Win cases from the late 80’s, early 90’s that have totally different internal shapes than newly manufactured Win brass.
I have several batches of Win and Rem brass that are within 2gr in weight of each other, BUT the Rem brass holds just shy of .2 CC’s less than the Win brass. Sectioning them shows that the web on the Win brass is almost double the thickness of the Rem brass, but the walls of the Rem brass are twice as thick as the Win brass.......this is where the capacity difference lies.
You are correct that some brass weighs more/less due to the extractor groove alone, but this is not always correct.
My example of the Win/Rem brass was illustrated on target before I sectioned or measured capacity, with the same load the dispersion on target was 8” at 300mtr. I figured due to the similar weight it would be much closer than that.....not so obviously.
Even famed consistent brass from Lapua has differed in capacity for me, due to the cost of it, I haven’t sectioned one to see the difference. Just can’t bring myself to cut one up. My last purchase of 6.5x47 was $228 for 100 cases!
Cheers.
