If you go to this BB's home page and scroll down to "other useful information", you can check out production for American sxs during the war. Not a lot was happening, although in the case of both Fox and Parker, they'd essentially stopped making doubles (at least the REAL Foxes) before the war started. SxS production at Ithaca and LC Smith wasn't much more than a trickle during the war, and Ithaca only made a few thousand NID's after the war ended. Only Elsie continued production of American classic doubles (along with the Win 21) in any kind of numbers after the war. So it's a little hard to judge how much was the impact of WWII and how much of it was the fact that sxs production was dying out even before Pearl Harbor.
As for the rest of American industry, the automobile companies shifted almost entirely to war production. My father was exempt from military service because he worked at John Deere. During the war, instead of making tractors, they made parts for tanks and planes.
There was also the issue that during the war, ammunition for civilian use was hard to come by. And many of those who might otherwise have been hunting or breaking targets were serving in the military.
