I thought some might be interested in the following pictures. I had cleaned the rifle and it needs a few shots to foul it so I stuck up a target in front of a peat bank. This is a 150 grain Hornady Spire Point from a 308 launched at about 3000fps. I shot 2 at 50 yards, 2 at 100 yards and 2 at 200 yards so I'm not sure what the range was. This was the biggest bit of metal I could find in the bank despite going quite deep, I did find quite a few sharp bits of copper from the jackets. My guess is that this bullet had maybe become upset from passing through the target and so might have struck the bank side on or at least somewhat unstable hence the fact that the lead core has entirely departed from its jacket. In saying that you can maybe just about make out that there appears to be something of a mushroom at what I suspect is the front end and there is an area where the lead is curled back similar to what you see in photos of ideal expansion, so perhaps this actually did strike head on. This was a flat based bullet with no hole in the jacket at the rear so there has been a considerable amount of energy at work here removing the core and fragmenting the jacket. I'm guessing that the other rounds remained more stable and had penetrated more deeply and so weren't found before I got fed up digging. I'd guess this one was about 2 feet down (well, across really) or so.
I've never recovered one of these bullets from a deer and have always been pleased with their performance so I don't consider this any indication that the bullet might "fail" on deer, only an interesting representation of the forces and energy at work when a bullet hits some sphagnum moss and a peat bank.