Testing at the range last weekend, I was able to reduce ES/SD significant from 10 FPS to about 6.7 FPS by using turned necks and lighter neck tension.
Summary
1. the first groups of all 3 configs all have bad ES. perhaps due to low case fill ratio? I removed A1, B1, C1 from all calculations.
2. the rest of the groups have SD ranges from 2-9 FPS, except for B5. it could be a process issue.
3. previously, neck thickness of 0.014" and NT 0.0035" has been tried with N565 + BR-2 and it has produced disappointing ES/SD. now neck thickness of 0.014" and 0.001" NT has also not performing. data suggests the gun does not like thick necks but rather thin necks when it comes to ES/SD.
4. previously neck thickness of 0.012" and NT 0.0025" has been tried with N565 + BR-2 and the average SD was 7.7 FPS. this run gives 6.72 FPS for N565 + 210M. this is the second time we see this neck thickness + NT combo work. for both of these groups, there is no negative velocity delta, indicating stable MV? for the 210M groups, all are below 18 ES and 8 SD. this neck thickness and tension is the combo choose.
5. looking at group Bs and Cs, any time MV is between 2850 and 2890, we have a good group. looks like the group size is determined by the MV not the charge weight. so C at 2870 FPS (74.2 gr) is the chosen charge weight.
6. 0.0015" tension is not stable regardless of neck thickness. something always goes wrong. for A, (with thicker necks), the speed deltas are like a roller coaster. for B, (with thinner necks), B5 has an SD of 13 and Velocity Delta is 24 FPS went going from B3 to B4.
Notes:
1. heavy bolt lift for many groups, even when shooting B2. this is the first time I'm hitting this and these charges are way below VV recommended max load. the only culprit I can think of is that this time, the shoulder length (2.1940") being only 0.0015" smaller than the max shoulder length of the fired cases (2.1955"). perhaps Magnum cartridges require 0.002" or longer shoulder bump?
2. choosing B (0.29 MOA) or C (0.43 MOA)? difference is 0.14 MOA
at 1000 yards
1000 yards 2870 fps drop -252.37"
if ES difference is +10 FPS, drop is -250.34", difference is 2" (0.2 MOA). so C is better.
if ES difference is +30 FPS, drop is -246.36", difference is 6" (0.6 MOA)
1700 yards 2870 fps drop -1033.60"
ES difference is +10 FPS, drop is 1025.3", difference is 8.3" = 0.45 MOA. C is much better.
ES difference is +30 FPS, drop -1007.83" difference is 25" = 1.5MOA
to do's:
- adjust seating depths with C
- try 12 rounds with no mandrel and no lube
- try 12 rounds with 215M
- try 12 rounds with White River LRP
- try 12 rounds with White River LRMP
