Next step?

ShtrRdy said:
So they are the same everything just a different day, and a lot warmer outside. ;-)
Click to expand...

Over on another website (6.5guys) they have a 10 shot load development that essentially argues the velocity of the bullet and not the charge amount or powder type is really what makes the load accurate. They argue any powder that (safely) duplicates a velocity will see an accuracy node at that velocity. So for your example, the additional 60* of temperature created more pressure which likely increased velocity. Based on my understanding, according to them, if you lower your charge amount just enough to get the velocity back where it was when colder, you're accuracy will return. Can anyone comment on this? I'm fishing for answers for the OP's second question, I guess. Haha. Of course some powders are a lot more temp stable than others, but it almost seems like gas for the car - you need a summer blend and a winter blend.
 
Update -- I did a few things based on everyone's suggestions and did some shooting this morning. This first target has two experiments on it.
20190705_115740.jpg
On the left most bulls-eye I tried a couple rounds using the 41.1 gr load to see if it would be anything like the original. It didn't match up too well.
On the center and right most bulls-eye i took Remmy700's suggestion and tried one more step up. The middle one is the same charge as before and the right one is 0.3 gr more. That looks very promising. I plan to load up some more like that and measure velocity with the Magnetospeed. These were with new Lapua brass so I'll need to tweak the load for once fired.

Another experiment I tried was to used the once fired Federal GMM brass and drop the powder charge a little to see if the group would improve. I used Quickload to give me an idea of how much to decrease it.
20190705_120642.jpg
Well, it turned out great such that the group size shrunk and the velocity was what I measured before. This did what ndking1126 suggested might happen. I have to admit the IMR-4064 is from a different lot of powder. It was the first 1 lb bottle I bought to try.
 
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ShtrRdy said:
Well, it turned out great such that the group size shrunk and the velocity was what I measured before. .
Click to expand...

That's really interesting, thank you for sharing! I know only one day at the range doesn't prove anything, but still good to see. Please keep us updated if you continue to shoot/tweak this load. I'd like to see if your experiences continue to line up with what they say should happen.

I'm curious, how much did you drop the load by? What increase in velocity did 60* result in?
 
Update : I settled on 42.0 grain of Varget for now and did some seating depth testing. Here's a picture of the results.
20190809_091520.jpg
Should I try +/- 0.005" around 2.840 next?
 
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When I started using Varget I ran a 12 round Satterlee test to look for a velocity flat spot and where the bullets were impacting. I went up to 44 grain which gave a velocity of 2706 fps. Those last few shots were getting scattered looking.
20190721_095900.jpg
The SAAMI spec says a 175 gr bullet should go 2600 fps.
 
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I tried varying the seating depth +/- 0.005" around the 2.840" length. Everything else is the same.
20190811_083153.jpg

The 2.840" length still looks the best.
 
Remmy700 said:
So 42 gr of varget with 175 smk. Man I am shooting 178s and I am running a ladder now from 43.5 thru 44.8. I think you can squeeze some more speed out of her brother.
Click to expand...

Remmy700 - would you mind sharing your results from this test?
 

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