Variation in velocity readings - Chronograph

[Walknby]

That is something else I hadn't considered. Thanks for the info. It will be interesting to repeat the loads with matching cases. I've bumped the load to 3.30 gns (N310) and hope to get out in the next few days. I'll try to do up some matching cases to try as well.

Out of curiosity I separated the range cases by head stamp and shot a group of 10 for each of Blazer, F.C. and R.P. I also shot a random group of 10 which would be a mixture of Blazer, FC and RP plus various unknown others. This is what I'd normally be shooting. (All of these are 147 gn 9mm with 3.30 gn vN310 and COL of 1.120)

Brand / Velocity / Power Factor
Blazer / 866 / 127
F.C. / 846 / 124
R.P. / 854 / 126
Random / 851 / 125

Brand / Spread / Standard Deviation
Blazer / 70 / 20.09
F.C. / 69 / 19.72
R.P. / 69 / 20.90
Random / 67 / 20.47

The spreads are very consistent. The lowest velocity was 813 in the random group and the highest was 898 in the RP group.

Thanks for all the input and interest. This was a good learning experience.