Regarding counterboring;
Pushing a lead ball through the bore doesn't reveal any looseness at the muzzle end.
I've succuessfully done the same thing with a Martini 12/15 with cleaning rod wear, and it worked wonderfully well.
Regarding rebarreling;
A rebarrel wouldn't keep the rear sight rib, the engraving, or the proof marks. Not important to making a "shooter", but important to the owner (and a reminder that this is not my rifle... ).
So rebarreling isn't a viable option for this rifle at this time.
The bore of this rifle isn't "a little frosty", or "has a little pitting"... it's a dark sewer pipe with indistinct rifling and lots of pitting.
The suggestions to get THIS bore to shoot are appreciated, and may well apply to other rifles. However, trust me... it's not gonna happen with this one.
Fat lady sung, put a fork in this bore... it's DONE...
I'll pass along all these posts to the owner!
Thanks again for the input!
Paul F.