I just started doing testing and an OCW with my 308 and IMR 4064. I have tested with a 20" Bartlein...I used my MagnetoSpeed V3 Speed Chronograph to develop the results.
175 Sierra Match King - 44gr IMR 4064 2.815"
Shot Speed
1 2658 ft/s
2 2658 ft/s
3 2656 ft/s
4 2656 ft/s
5 2652 ft/s
6 2651 ft/s
7 2650 ft/s
8 2649 ft/s
9 2647 ft/s
10 2646 ft/s
11 2643 ft/s
12 2640 ft/s
13 2637 ft/s
---- ---- ----
Series 2 Shots: 13
Min 2637 Max 2658
Avg 2649 S-D 6.74
ES 21
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178 Hornady AMAX - 44gr IMR 4064 2.815"
Shot Speed
1 2645 ft/s
2 2642 ft/s
3 2639 ft/s
4 2638 ft/s
5 2637 ft/s
6 2637 ft/s
7 2634 ft/s
8 2627 ft/s
9 2614 ft/s
10 2613 ft/s
---- ---- ---- ----
Series 3 Shots: 10
Min 2613 Max 2645
Avg 2632 S-D 11.1
ES 32
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155 Hornady AMAX - 44gr IMR 4064 2.815"
Shot Speed
1 2740 ft/s
2 2735 ft/s
3 2721 ft/s
4 2721 ft/s
5 2714 ft/s
6 2712 ft/s
7 2706 ft/s
8 2702 ft/s
9 2695 ft/s
10 2693 ft/s
---- ---- ---- ----
Series 2 Shots: 10
Min 2693 Max 2740
Avg 2713 S-D 15.7
ES 47
When I took out my 24" Rock I took it to 44.4 grains and was just under 2750fps with my OLD CED Chrony so I will have to check it out with my MagnetoSpeed V3. BTW, I am loving my new Chronograph if you can't tell. Awesome device. Anyways, I like IMR 4064 as it seems pretty temp insensitive but I will know for sure this summer when it gets hotter.