Denton,
It's entirely possible that you are correct but it still doesn't make sense on why it's happening now vs. why it's never happened before.
I started handloading this bullet at the beginning of the year in January, in weather comparable to what we experienced yesterday. The first loads I tested were this exact same powder, primer, case, and bullet but at 40.0g of H4895. My notes show that load was tested on January 29th at 10:30am and the weather was 30F, nearly identical to the weather at the range at the time I was there yesterday.
Also, In Janurary the case was brand new and not previously fire-formed to my chamber. IIRC, the cases grew on average of about 0.030" upon firing, so I know there was no shoulder engagement at all when loads 7.0g lighter were fired in similar weather. These cases were once fired and neck sized using a Lee Collet Die so the shoulder should have had a much better seal than previously, but this load and lighter loads have never done this before.
Also, H4895 is one of Hodgdons Extreme powders and is supposed to be less sensitive to colder temperatures.
Lastly, why would the other shot that dented the case show ~150fps higher velocity than all the other shots in that string? Wouldn't that imply greater pressure on that shot vs. the others?
I'm just stumped. But I do appreciate any and all feedback.
