Load development issue

I’ll start by stating I’m fairly new to reloading.
I am currently working on a load with ADI2208, CCI 200, Hornady 139SST after having no luck with RE17.
I shot a ladder a couple of weeks ago with the following range of charges.
39.5
40
40.5
41
41.5
42
42.5
42.8
43
43.2
43.5

Groups were tight between 42.8 and 43.2 with 43 and 43.2 being very close. I only shot one ladder, and then 42.8,43,43.2 from the second ladder to see if I got the same results. I did, so opted for 43.1.
In hindsight I think I should have kept 42.5 in the mix as there were 4 holes touching on the first ladder. Probably focused on the hotter load too much.

First image shows a portion of the first ladder - 42.8-43.2 group
Attachment 17365

Second images shows partial ladder 42.8 - 43.2
Attachment 17366

Anyway, based on the findings of the ladder, I loaded some more rounds at 43.1, and started to experiment with seating depth. .02, .03, .05. They were all disappointing as were the rounds that were set to the same as the ladder’s seating depth.
I was shooting off someone else’s rest, not my usual sandbag, but I don’t think that’s to blame.

Third image shows those results, the top 2 groups are at 43.1 - seating as per ladder.
bottom left is at .05, middle is .03, right is at .02
Attachment 17367


What is the next step?
Re try off sandbags?
do OWC at 1g intervals between 42.5-43.2?
Should I just start over with the full OWC method?
Any thoughts or advice would be appreciated.

I take it you are shooting 7mm08 ?

OCW is normally in increments of either 1% or 0.7%, which for your loads should work out to about 0.3gr steps.

Remember to shoot round robin, and allow time to barrel to cool between strings.

I do OCW, get an idea of best load first (least movement in terms of point of aim, not group size) and then play with seating depth to tighten the groups.

KISS question, are you using brass that has been fired in this rifles chamber ? How are you sizing and trimming ?

Perhaps different environmental factors fooked with the 2nd test?

Two ladders with similar results, 4 adjacent charge weights touching in that first ladder pictured, supported by the second ladder, then it all flies apart very badly with 2x three-shot groups at the centre charge weight and at the same seating depth. It has to be something else that has changed between the two outings, and changed very quickly rather than progressively. Obvious stuff first - I'd be back to shooting off my own bags for starters. I'd also be inclined to then stick with c.43gr (at whatever jump the ladder testing was at) until the problem is IDed before chasing further refinement.

Would sort of stock have you got? Something nice and stiff or soft and flexible?

Does the rifle shoot factory ammo OK? Has it ever shot OK? Are you a competent shooter? Not meaning to be harsh but a 1" shooter cant expect 1/4" groups.

ebf, Yes 7mm08.
it is all twice fired brass from this rifle.
I have been doing minimal resizing "partial full length", trying to keep it close to my rifles chamber with standard FL dies. Chambering is fine.
I don't have a headspace gauge.
Trimming with the standard lee case length gauge.

Beavis, I don't think there was anything significant. No real wind, temperatures were not significantly different, and its only over 100m.

right, then I think Puffin is onto it, back to your own bags / supports - that seems to be the only obvious difference...

Puffin, I will retry off the sandbags hopefully over the weekend at 43.

Upland, standard T3

Kiwijames, yeah sub moa with most factory ammo. I think I'm average, never done 1/4 moa but can do between 1/2 and 1moa consistently . The ladder groups were around 1/2.

Quote:

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Originally Posted by ebf

right, then I think Puffin is onto it, back to your own bags / supports - that seems to be the only obvious difference...

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I hope that's it. Hopefully have a go this weekend. Thanks for the feedback.