Load work up: Group size vs ES/SD

[Bad_Donkey]

I went to range today with a load work up with my 7mm-08 using Hornady 162 gn eld-m. Which do you think is more important, absolute group size or low es/sd numbers? My best load as far as lowest es/sd numbers was also my largest group size. Maybe that was because of me, not sure. I'll post the results below. Which group would you choose to load? I'm learning towards group #3 and maybe increasing by .1 gn., as there was a downward trend in ES as the load increased. All groups are 5 rounds each. There is a .3 gn difference between the loads.

Load #1: Avg. Speed: 2654 ft/sec
ES: 18
SD: 7.1
Group size: 1.09"

Load #2: Avg. Speed: 2680 ft/sec
ES: 17
SD: 5.9
Group size: .640"

Load #3: Avg. Speed: 2702 ft/sec
ES: 16
SD: 7.25
Group size: .650"

Load #4: Avg. Speed: 2722 ft/sec
ES: 12
SD: 5
Group size: 1.455"

 

[morganlamprecht]

the truth is with sample sizes that small for ES/SD, those numbers mean almost nothing being that close together....theyre all close enough to be a wash when taken with a larger sample size

i look for the group size/consistency...good ES/SD numbers follow quality components and solid reloading practices for me

 

[Pvt.Donut]

Depends on what you plan to shoot.

Shooting 600 yard F-Class, do load development to get the smallest groups at 600 yards.

100 yard benchrest? Shoot for smallest group at 100 yards.

I've always been a fan of other a traditional ladder test or the Satterlee 10 Shot Method for determining powder charge. Then I tighten up groups with seating depth. I don't like fully weighing out every charge weight exactly so I find a window that allows me a low SD if I drop powder high or low.

Also, 5 shots typically aren't enough to validate SD's. You will want at least 10 shots.

 

[Snuby642]

Going to sit in and see what experience says compared to my limited reloading time .

 

[Bad_Donkey]

the truth is with sample sizes that small for ES/SD, those numbers mean almost nothing being that close together....theyre all close enough to be a wash when taken with a larger sample size

i look for the group size/consistency...good ES/SD numbers follow quality components and solid reloading practices for me

Depends on what you plan to shoot.

Shooting 600 yard F-Class, do load development to get the smallest groups at 600 yards.

100 yard benchrest? Shoot for smallest group at 100 yards.

I've always been a fan of other a traditional ladder test or the Satterlee 10 Shot Method for determining powder charge. Then I tighten up groups with seating depth. I don't like fully weighing out every charge weight exactly so I find a window that allows me a low SD if I drop powder high or low.

Also, 5 shots typically aren't enough to validate SD's. You will want at least 10 shots.

Ok. Given the above, what would be your next step? Should I load up 10 rounds of each and retest? I don't shoot competitions. I normally just casually shoot prone from 100 to 600 yards. I hope to find somewhere I can shoot a little farther, but not many options around here.

 

[morganlamprecht]

id load up some to test between #2 and #3 and look how the entire window shoots

looking at group accuracy/consistency and velocity across the range

if you wanted to tweak it further you could start playing with seating depths also

 

[Snuby642]

^^^^ this

 

[Bad_Donkey]

id load up some to test between #2 and #3 and look how the entire window shoots

looking at group accuracy/consistency and velocity across the range

if you wanted to tweak it further you could start playing with seating depths also

Charge increments were .3 gn. Seating depth was close but not touching the lands. This rifle seems to have a some what of a short throat. These eld-m's will touch the lands well before I get to mag length.

 

[morganlamprecht]

seating depth works both ways...if youre already near the lands, you can work back off of them

 

[just browsing]

Charge increments were .3 gn. Seating depth was close but not touching the lands. This rifle seems to have a some what of a short throat. These eld-m's will touch the lands well before I get to mag length.

Try to avoid “just touching” or “kissing” the lands...

If you’re going to jump them, JUMP them. Like 5-10 thou minimum. Same for jamming. The in-between lengths are more difficult to predict and can have a greater impact on changes of speed or how a specific load shoots. 10 thou jump should shoot the same as 12 thou jump all else being equal, but 2 thou jump could actually contact the lands depending on your tolerances.

 

[Bad_Donkey]

seating depth works both ways...if youre already near the lands, you can work back off of them

Try to avoid “just touching” or “kissing” the lands...

If you’re going to jump them, JUMP them. Like 5-10 thou minimum. Same for jamming. The in-between lengths are more difficult to predict and can have a greater impact on changes of speed or how a specific load shoots. 10 thou jump should shoot the same as 12 thou jump all else being equal, but 2 thou jump could actually contact the lands depending on your tolerances.

I checked my notes and these rounds were about .008" off the lands. Not sure I want to go much closer, but maybe after settling on a charge weight I'll play around with seating a little deeper. The bullets are already fairly deep in the case though as the COAL is only at 2.852" and base to ogive length of 2.165".

 

[pbatesaz]

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