Anyone have any idea what might have caused the uniform pattern of marks on the land and groove on the near side of the second photo?
They look like they continue all around the bullet...
I suspect that slug came out of a jacket, the jacket being the impressing force which transferred the land impressions to the core.
I think the land engravings on the bullet are too sharp to have been transferred through a jacket. Under magnification there are numerous full-length straitions that I do not think would show the same way if they had been in a jacket. I stick with the notion the bullet was a semi-wadcutter design with a hard shoulder and a solid crimp.
It definitely looks like a swaged slug of some sort. I have seen some surprisingly sharp rifling impressions on the slugs of bullets which have been shed. A relatively thin-jacketed handgun bullet is sometimes so inclined. I would think that the gun's lands would have scraped their typical striations into the lead had the slug been exposed to the bore. There are too many manufacture marks on that slugs still visible to think that rifling striations would have been smoothed by time or chemical interactions. But, as with so many things so related to these brief impacts, there is often mystery that isn't readily obvious immediately.
