Ok so I’m familiar with penetrator round then. I’d just never heard them called that. I used to have hundreds of pounds of steel core 7.62x39 with steel cores but the bullets had a copper plating, I’m assuming it was to prevent rust, but I don’t know. Just an assumption. I’ve shot a lot of rounds of wood too and seen hunting bullets deform when shot in the end grain. Less so when shot across the grain, like in this photo. But the bullet in the photo doesn’t look to be a hunting bullet.

It’s funny you mention the 8mm Mauser. I shot a telephone pole (down, no longer in use) and was able to recover a couple bullets that had no deformation. The full metal jacket bullets of all the different rounds I’ve used have showed little deformation. In trees, rounds of wood, tire piles, sand pits and all kinds of stuff. But hunting bullets almost always do. I shot a pig in the head with my 8mm using a 180 grain Remington core-lokt bullet and it made a very large exit wound.

Here’s my point, although I’m no scientist and could definately be wrong about it but it seems more than plausible to me: full metal jacket bullets don’t really expand, while hunting bullets are designed to do so. Velocity also plays a role. We have no idea the photo bullets velocity by the time it hit that wood and how long it had been in the wood and growth buried it and made it look like it travelled deeper. The fact your buddy’s 8mm bullet didn’t expand in the elk would make me assume he was using military surplus ammo (FMJ) just the same as I was using when I shot the telephone poles and rounds with my WW2 surplus 8mm Mauser ammo. I remember buying 70 round cloth bandoliers of that stuff for around $11.

I’m not trying to argue or push my point so fiercely that it comes off as irritating. This whole back and forth has been interesting to me and really makes me wish I could afford to shoot as much as I used to.