There were certainly a lot of Continental makers still turning out 2 1/2" guns prior to WWII. The difference to which Burrard was referring may be that some Continental makers (Sauer and Francotte are a couple that come to mind) were exporting quite a few guns to the United States prior to WWII--at least quite a few compared to the British shotgun industry--and when they did so, they catered to changes in the American market. As in from short shells to what became the 2 3/4" standard. But many guns that stayed in Europe continued to be chambered for 2 1/2" shells.
Patrick, the British continued to turn out 2 1/2" guns following WWII. Some of the Webley and Scott 700's, for example--a model that did not appear until 1947--were 2 1/2" guns. It's not even all that easy to state exactly when the change occurred in the States, because all manufacturers did not change at the same time, nor did individual manufacturers change all gauges at the same time. For example, LC Smith switched to 2 3/4" as the 12 and 20 gauge standard some years before they did the same in their 16ga guns--which remained short chambered until at least 1939 or 1940. About the only blanket statement that can be made re American guns is that it's not likely any short-chambered guns were produced after WWII, although that does not preclude the possible sale of the occasional leftover short-chambered gun from pre-war days.
