I can't honestly say that I have seen a "shot out" oval bore
as those people who couldn't get them to shoot I figured didn't know how to - after meeting a couple of people who could / did get them to shoot.

However, from what I have seen, in some oval bore barrels you can clearly see the sprial of the oval bore - or the way the light reflects off it - whereas in others, their is still some sprial but not nearly as defined.

Whether this is differences between the makes I am not sure but it may give you some indication.

And in regards to shooting, those people who have worked it out have generally not found a problem.

Hope this helps. If I get a chance I will ask one of the owners how he views the barrels for wear.