Ran some loads across my LabRadar as I was shooting to see how they grouped, and also ran an IMR ladder.
338 Norma Mag
26" Bartlein 1:9.3 twist
Brass: Peterson (once fired)
Primer: Fed 215
Bullet: 275 grain BDII
Charge 87gn H1000 - two strings of five
1. DNR
2. 2796 fps
3. 2826 fps
4. 2786 fps
5. 2782 fps
Second string (ES of 12.13 and SD of 4.99)
1. 2790 fps
2. 2796 fps
3. 2784 fps
4. 2786 fps
5. 2785 fps
87.3 g H1000
1. 2815 fps
2. 2833 fps
3. 2839 fps
4. 2813 fps
5. DNR
IMR 7977 Ladder (virgin Peterson cases)
Charge/ Speed
79gn / 2534 fps
79.3 / 2551 fps
79.6 / 2539 fps
79.9 / 2547 fps
80.2 / 2560 fps
80.5 / 2570 fps
80.8 / 2563 fps
81.1 / 2594 fps
81.4 / 2596 fps
81.7 / 2629 fps
My twist rate is "marginal" on the Berger calculator, but I've shot tight groups out to 800. Wasn't impressed with today. But, it could have been me. Target was at the 300.
First target is from my normal hunting load of 86.9 grains of H1000. Average for that was 2750fps when I developed it. I did shoot this string pretty fast. All five shots in under three minutes.
Second is from the 87 grains of H1000. Seating depth on the 87 grains was not the same as the 86.9 grain shot group.
Going to work on the IMR 7977 some more and mess with the seating depth to tighten up the groups a little.