So.... just how hot is a bullet when it leaves the barrel?

[rockrat]

Possibly there was some moisture in the bullet jacket when the core was seated. Pressure would have kept the core in place, going down the barrel, but once hitting the atmosphere, the steam pressure caused the core to back out.

Otherwise, the moisture getting in the bullet and frost/freezing driving the core out would be the only other explanation that I can think of. The lead does look a bit oxidized, like its been sitting there awhile.

We get the rocks in the fields around here, after every winter. Its called "frost heaving".

[Bullshop]

Extremely cold temps will cause lead cores to extrude from a jacket in that manner when left out over a long period of time. I have found loaded ammo that had been lying on the ground for many winters that had the lead core extrude in this manner but move forward to the open end of the jacket. I suspect we are looking at FMJ jackets where the open end is the base.
I see you are from Idaho so assume it gets cold enough there to cause this.
I cant say for sure this this is the case with your recovered bullets but just saying that it is a cause.

[Geezer in NH]

Jacketed bullets bend like the pic's especially the FMJ's that's how they wound without expanding.

I don't get the humanitarian **** of the Hague convention banning expanding bullets. Getting hit by any is bad. (note the USA never signed it)

[Grump]

Dirt berm + rear-heavy bullet=a bootleg turn in the dirt and usually some amount of deceleration base-first. I *believe* that the open air above the slope makes this happen in a shorter distance than you see in those jello pics of bullet travel, yaw, and tumbling. Asymetrical resistance and all that.

I also would not put too much stock in the observed level or lack of visible oxidation as an indicator of exposure time in the berm, not without some controlled testing and careful observation *for that specific alloy*. One of my quick ways to tell whether a soft lead ingot got mixed in with the harder allow stuff that's been sitting around for years is the color--IME the soft stuff BHN 8 and less tends to go blacker and change color much faster than the harder alloys. Speer told me once IIRC that their cores are 3% antimony, which I believe is enough to really show down the oxidation rate. So maybe they still could be winter frost-processed lead turds oozing out of those jackets, having received a good head start from jacket slow-down and beginnings of separation on impact.

Occam's Razor points to frost and checking the hardness of the cores might push the evidence further in that direction...

Oh yeah, Idaho. It doesn't get warm enough long enough there for lead to oxidize, so there!!!!! I'm right, I'm right, I'M RIGHT AND YOU KNOW IT!!!!!