Powder charge vs temp fluctuation and accuracy

[HairyScandinavian]

So I found a decent load for my 6 ARC AR15, 29gr of Lever shoots consistently better than 29.5gr with 95 TMK's. I'm happy with it. So it's been 80's and 90's here while testing so speeds are elevated with Lever being pretty temp sensitive at the higher end of temps. My question for those of you with more experience than me is when the temperatures drop and the 29.5gr slows down to the speeds I'm getting with the 29gr now, will the 29.5gr inherit the 29gr's accuracy with the slower speeds or will the 29gr stay the better charge going slower than it is now?

Please don't tell me I'll have to try it or it'll be February before I know.

 

[Taudisio]

So I found a decent load for my 6 ARC AR15, 29gr of Lever shoots consistently better than 29.5gr with 95 TMK's. I'm happy with it. So it's been 80's and 90's here while testing so speeds are elevated with Lever being pretty temp sensitive at the higher end of temps. My question for those of you with more experience than me is when the temperatures drop and the 29.5gr slows down to the speeds I'm getting with the 29gr now, will the 29.5gr inherit the 29gr's accuracy with the slower speeds or will the 29gr stay the better charge going slower than it is now?

Please don't tell me I'll have to try it or it'll be February before I know.

Possibly.
The bullet is leaving the barrel at precise timing with the barrel vibrations to give you the best accuracy and that could be your “accuracy node”. You should test it.

I did a test with my arc and lever. I posted it on another thread that I can’t remember, but you can easily replicate it with your loads and test for yourself.

I loaded up 10 identical rounds. Shot a 5 round group with ones that were at ambient temperature. The second 5 I left in the freezer two days prior, pulled the ziplock of rounds out, filled another ziplock with ice and stuffed the one with the 5 rounds inside like a little cooler. 10 minutes up the mountain. Shot back to back groups.
The frozen group shot high right and opened up. It’s late and I don’t have my notebook, but it was like 55 or 60 degrees out, and the velocity change was less than I expected. I assume the frozen rounds were around 20-30 degrees and the difference was 40fps or so IIRC. 2730ish vs 2690. I’ve seen the same load up past 2750 when it’s warm out. Based on my previous data-2695 was my avg for the charge a half grain lower.
It isn’t perfect science, but I got real, notable, results anyway. Throw 5 rounds of 29.5gr in the freezer and shoot them cold next to your warm temp load. I am very curious and would try to do the same with mine to see if the results match.