N.R. Davis, like all the U.S. double gun makers, sourced the majority of their "rough forged tubes" or "rough bored tubes" from Belgium, from Cockerill steel.
The tubes were rebored, chambers cut, joined and finished by the U.S. makers.
.700 would be about 18.0 mm
I've looked through a bunch of period resources but couldn't find the typical bore of the "rough forged tubes" but suspect 18.0 is pretty close.
I'm aware of a Crescent that slipped through never having been rebored with a bore of about .700
I assume the bore did appear to have been finished?
Maybe a bad day (or the day after St. Patrick's Day?
) in the barrel dept.?
http://books.google.com/books?id=QDk...AJ&pg=PA879&dq
STATEMENT OF MR. THOMAS HUNTER, OF FULTON, N. Y., REPRESENTING THE HUNTER ARMS CO. AND OTHERS
The Chairman. Will you state the companies you represent, Mr. Hunter.?
Mr. Hunter. The Hunter Arms Co., the Baker Gun & Forging Co., Parker Bros. Gun Co., Hopkins & Allen Arms Co., A. H. Fox Gun Co., Lefever Arms Co., H. & D. Folsom Arms Co., Ithaca Gun Co.,
N. R. Davis & Sons, and Harrington & Richardson Arms Co.
Senator McCumber. Does the American manufacturer use the unfinished importation?
Mr. Hunter. He uses what are designated in the present bill as "gun barrels rough-bored." That is what we import.
Senator McCumber. To what extent do you use those?
Mr. Hunter. Entirely.
Senator McCumber. You do not manufacture any of them?
Mr. Hunter. No, sir.
We have no facilities for making shotgun barrels.