I ran some weights. The average weight of 7 cases of each (with fresh primer):
Winchester 235.8 gn
Norma 250.9 gn
for a difference of 15.1 gn of brass. Since brass has a density of 8.73 g/cm3 and water is very close to 1, the capacity difference is 15.1/8.73=1.73 gn of H2O - WOW.
So how much powder is that? Approximately 1.5 - 2 gn?
I loaded up 6 charges with Norma brass, 165 TTSX, and Superf; 68.5 - 71.0 in 0.5 gn increments approx 60 thou off the lands. I stopped when I could no longer hear the powder move in the case. I decided I did not wan to compress it - much.
I will be at the range tomorrow morning. I am setup to load in the back of my SUV.
Checking BTO on all the bullets, 44 out of 50 were 1.045 - 1.055". There were less and three were more. Those 6 were used in the loads above. I will then look at the results of my
"mini ladder" and decide what to load next.