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A Word about my process. There are two goals in mind. One is to find the charge that will have the lease change in velocity between rounds that are plus or minus .2gr for the target charge. The other goal is to find the charge that is tuned to the rifle such that the groups are very tight. These two goals do not necessarily include each other.

I loaded up 50 rounds of 6.5 Creedmoor using H100V - a hybrid powder that is very tolerant of temperature. I discovered that the IMR4350 that I have been using for decades will increase 70 ft/sec for every subsequent round, gaining hundreds of feet per second over a 10 shot group with my 270 hunting rifle. I never knew that because I never had it over a chronograph before. Also, I did not shoot many rounds at a time because most hunts had one shot kills and so as long as the first shot is completely predictable, all is well I guess. Having said that, when my IMR4350 is shot up, I will be doing a similar exercise with both my 270 and 300 mag - 

Here is the data I collected on my workup for the 6.5 Creedmoor:

(10) 5 shot groups

6.5 Creedmoor 143g Hornaday H100V powder   CCI200 New Hornaday Brass  
1 2 3 3 5 powder chg average deviation spread min max  
2744 2749 2777 2743 2744 41.4 2751.4 12.97074 34 2743 2777 1
2765 2821 2794 2787 2824 41.6 2798.2 22.04904 59 2765 2824 2
2784 2778 2768 2777 2775 41.8 2776.4 5.161395 16 2768 2784 3
2771 2780 2785 2784 2784 42 2780.8 5.192302 14 2771 2785 4
2794 2792 2798 2798 2823 42.2 2801 11.24278 31 2792 2823 5
2813 2808 2822 2842 2827 42.4 2822.4 11.8423 34 2808 2842 6
2848 2825 2824 2873 2861 42.6 2846.2 19.40515 49 2824 2873 7
2871 2902 2873 2852 2851 42.8 2869.8 18.54077 51 2851 2902 8
2865 2838 2819 2824 2809 43 2831 19.40103 56 2809 2865 9
2861 2815 2838 2833 2856 43.2 2840.6 16.57227 46 2815 2861 10

From the table, 42 grains has only 14 fps spread and a standard deviation of 5.19 - really excellent!!

 

One thing that always surprised me was how you could have more powder and the bullet can move slower - here are graphs to show the results

here are the targets showing groupings at 100 yards

I got lucky on this one the best consistency is also the best tuned for the barrel - for the most part ...