Working up loads for my grandsons Kimber 84M in 7-08. Once fired Lapua brass FL sized and bumped .002. CCI BR2 primers. 140g Nosler Partitions seated .03 off. H4350 powder weighed on a Gem scale. Looking for nodes and can't make heads or tails out of the results. Candidly, I'm not sure I see any nodes at all. Ammo assembled at the same sitting. Ran two tests for confirmation. Anybody experienced this before?
Load. A. B
45.6. 2809 2803
45.8 2820 2826
46.0 2842 2817
46.2 2853 2818
46.4 2856 2838
46.6 2897 2839
46.8 2892 2827
47.0 2879 2913
47.2 2894 2945
47.4 2920 2917
47.6 2894 2887
Oofta! These are some muddy waters kind of results. Frustrating I'm sure. Several things come to mind here:
1) chronograph error. Could the Magneto Speed have been or wiggled a little loose or just setup too close or far from the bore?
2) Bearing surface variations. Did you sort bullets for this?
3) Seating depth. In my experiences with Nosler ABLR's they're known to be pretty soft and like a bit more jump. Loaded too close and you may see inconsistencies. I've been told that the Partition construction is similar to the ABLR so is it possible that 0.030" jump is too close?
4) Primers. Could a switch here show more consistent ignition?
5) Powder. It's possible that this combination of brass, bullet, powder, primer, and gun just don't work as expected. Though all are high quality components, they just might not be the best recipe. Switching to a faster or slower powder might make ignition more consistent.
6) Neck tension. This can be critical in consistent velocity. Lapua brass is known for its consistency but have or can you check it?
Looks to me like it's worth testing again. I'd start by sorting bullets by bearing surface, then checking the neck tension and possibly turn them if you thought it was a factor, then check seating depth at the ogive. When it's time to shoot I'd be triple sure the magneto speed is setup perfectly. I would also load 3 per charge and use the average velocity as that's the basic minimum for scientific data. If your results are erratic again after that test it would seem time to swap primer and/or powder components. I wish I could give you a more expedient or economical answer but this data is just too erratic to glean any info from in my opinion. Check your component consistencies and give it another go. Good luck and keep us all posted. Here's hoping we can all learn something.