Something funny while doing load development

[shell_guy]

Hey guys, working on some load development for my 5r .308 and I have notice a trend with my hotter loads. It would seem that my first 2 shots in a group are consistent and tight and my second 2 shots are also tight but have a distinctly different POI. Rifle details:
700 R5 .308
Bedded in McMillan A5
Bipod
ATRS Rear pack
Vais Brake
Sightron Siii 8-32
20moa ATRS Rail and ATRS rings

Rifle will shoot .3-.5 MOA with FGMM.

I did an OCW test a week or so ago, picked my 2 best charge weights, then I added .2gn to each of those.

Taget and load details: All shoot with Berger 168 Hybrid and CCI Br2 primers
Load 1 Load 1 Load 2 Load 2
Load 3 Load 3 Load 4

Load 1 - N550 45.6gn
Load 2 - N550 46.7gn
Load 3 - N550 47.0gn
Load 4 - N550 47.2gn (over max, no pressure signs)

I would just assume that it is the shooter pulling the shots, but it seems strange to me that I would pull 2 shots so consistently.

 

[FunkBass2008]

That is interesting. You're right, it does look like there is some consistency to the two & two patterns. Are all the shots being taken with similar timing intervals?

and did you load the batches in groups or one at at time?

Maybe if you had another shooter shoot the same loads to see if you can isolate the shooter variable..?

 

[Surgikill]

Try shooting round robin and see what happens. Maybe barrel heat? Or the round absorbs heat from the action while it's chambered increasing velocity?

Sent from GS3 Synergy

 

[shell_guy]

That is interesting. You're right, it does look like there is some consistency to the two & two patterns. Are all the shots being taken with similar timing intervals?

and did you load the batches in groups or one at at time?
Loaded individually, new Lapua brass sorted by case weight, Forester BR die. Shots taken with 5 mins between groups and 30 seconds between shots.

Maybe if you had another shooter shoot the same loads to see if you can isolate the shooter variable..?

Try shooting round robin and see what happens. Maybe barrel heat? Or the round absorbs heat from the action while it's chambered increasing velocity?

Sent from GS3 Synergy

Heat is about the only thing I could think of.
OAT was 46 degrees and zero wind.
All are 4 round groups.

 

[Surgikill]

Fwiw I have had the same thing happen. It could also be trigger pull? Shooting at the crest of one breath cycle and the valley of another? Just throwing some ideas out there

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