Seekins Havak Element 6.5 PRC 21” with TBAC Ultra 7
Berger 156 Elite Hunter, N565, Federal GM210M primers, Lapua Brass twice fired, 0.002 headspace
CBTO: 2.347” (.010 off lands)
I’m coming to the end of the powder-charge portion of my load development and not sure where to go from here. I think I found a good velocity node from 58.3 to 58.6gr. Each charge weight in that string have good ESs and SDs. They are right below where I start hitting some minor pressure signs. Really happy with the velocities but I’m not sure which charge weight to use as I move on to adjusting seating depth.
Below is the data I’ve collected from these 4 successive charge weights. I know I’m only focusing on velocity right now but I’ve included the group sizes at 200 yards just in case it influences anyone’s advice. The group data are split up because they were shot on different days instead of all at once, so I measured them separately. There are also different number of shots because I initially wanted to stop at 58.4 but 58.3-58.4 shot so well I thought I'd go a bit farther with 58.5-58.6 to see if the node was bigger, which it definitely was. So I know it's not apples-to-apples comparison since there are a different number of shots for each, but I'm working with what I have right now:
So options I'm thinking:
1. Go with 58.3gr because 1) it has the best ES/SDs considering/in-spite-of the larger sample size, and 2) it is in a VERY flat spot between 58.2 and 58.3. Cons: its at the beginning of the node and the charge weight just below it (58.2gr) had erratic velocities and the worst group
2. Go with 58.4gr because ES/SDs are fantastic and its in the middleish of the node
3. Go with 58.5gr because 1) it also is in the middle of the node, 2) also has great ES/SDs, 3) it has identical average velocity to 58.5, so it seems like a flat spot, 4) group wasn't bad, and 5) it has the highest velocities, and I'm trying to get every fps I can (wow...there are so many reasons here this seems like the way to go lol)
4. Go with 58.6gr because ES/SDs are decent and it has the best group (I know, 5 shots is a VERY limited set of data...your groups are too small...and I'm in the charge weight portion of load development but damn its tempting to go chase the small group)
So which of these options should I go with? Bonus question: As I move on to seating depth, what kind of increments should I test? I'm .010" off the lands now. So go back .005, .010, .015, or more?
Thanks in advance!
Berger 156 Elite Hunter, N565, Federal GM210M primers, Lapua Brass twice fired, 0.002 headspace
CBTO: 2.347” (.010 off lands)
I’m coming to the end of the powder-charge portion of my load development and not sure where to go from here. I think I found a good velocity node from 58.3 to 58.6gr. Each charge weight in that string have good ESs and SDs. They are right below where I start hitting some minor pressure signs. Really happy with the velocities but I’m not sure which charge weight to use as I move on to adjusting seating depth.
Below is the data I’ve collected from these 4 successive charge weights. I know I’m only focusing on velocity right now but I’ve included the group sizes at 200 yards just in case it influences anyone’s advice. The group data are split up because they were shot on different days instead of all at once, so I measured them separately. There are also different number of shots because I initially wanted to stop at 58.4 but 58.3-58.4 shot so well I thought I'd go a bit farther with 58.5-58.6 to see if the node was bigger, which it definitely was. So I know it's not apples-to-apples comparison since there are a different number of shots for each, but I'm working with what I have right now:
| Charge weight | # of shots | Avg Velocity | ES | SD | Groups at 200 yards |
| 58.2gr | 6 | 2863 | 26 | 9.9 | 6 shot 1.5 moa |
| 58.3gr | 11 | 2860 | 11 | 3.9 | 6 shot 1.46moa (.81moa with 1 flyer), 5 shot .86 moa |
| 58.4gr | 8 | 2865 | 8 | 4.7 | 5 shot 1.0moa, 4 shot .74moa |
| 58.5gr | 5 | 2873 | 12 | 4.9 | 5 shot .96moa (.61 moa with 1 flyer) |
| 58.6gr | 5 | 2873 | 16 | 7.3 | 5 shot .57moa |
So options I'm thinking:
1. Go with 58.3gr because 1) it has the best ES/SDs considering/in-spite-of the larger sample size, and 2) it is in a VERY flat spot between 58.2 and 58.3. Cons: its at the beginning of the node and the charge weight just below it (58.2gr) had erratic velocities and the worst group
2. Go with 58.4gr because ES/SDs are fantastic and its in the middleish of the node
3. Go with 58.5gr because 1) it also is in the middle of the node, 2) also has great ES/SDs, 3) it has identical average velocity to 58.5, so it seems like a flat spot, 4) group wasn't bad, and 5) it has the highest velocities, and I'm trying to get every fps I can (wow...there are so many reasons here this seems like the way to go lol)
4. Go with 58.6gr because ES/SDs are decent and it has the best group (I know, 5 shots is a VERY limited set of data...your groups are too small...and I'm in the charge weight portion of load development but damn its tempting to go chase the small group)
So which of these options should I go with? Bonus question: As I move on to seating depth, what kind of increments should I test? I'm .010" off the lands now. So go back .005, .010, .015, or more?
Thanks in advance!
