I have some ballistic data for the 57mm tank gun from which trajectory curves might be calculated, but I'm not sure that would prove anything.

There was also an aircraft gun which fired the same basic ammo (same case, different loads) but hardly any of them (if any) saw service.

Those posts answer the question, I guess. I thank you: that'll save endless stewing.

I'll just present the information I've accumulated and leave it as another 'imponderable'.

I've attempted to finalize my webpages on this subject, but am of course still interested in feedback. There are some topics which I leave open: some seem more effort than is warranted; others can have no answers; a metal detector is on order as a long shot.

I appreciate the direction I've received from various contributors on this forum.

My treatment of this subject has grown to 11 webpages (which start here), and offers more detail than the average reader probably cares to wade through. As a result, I've started the subject off with a single page condensation --- it's a long page, but just one.

I know this may be a little simplistic, but have you asked the people in the local area? It's possible that you might even find an eye witness allowing you to determine when and, possibly, what. I've found the typical Thai to be a friendly, intelligent person willing to help when shown just a little respect.

I'll give you holes! How many? How big?

Fair question. Yes. I was directed to one elderly local, who speaks some English, of all things. But unfortunately he didn't know anything about the holes.