It is a fact that steel was used by most of the ammunition factories for case production, either the entire case in the instance of metallic rounds, or case heads for shotgun shells, in 1944 and 21945. They were sold that way also in the very little commercial production that was going on. I don't know off hand if Federal was doing any commercial production at all in that period, but if they were, the shotgun shells would probably be with steel heads. Honestly, off hand, I don't recall if they were even doing military production. Am drawing a blank on that for some reason.
Remington produced steel shotgun shells, according to their little wartime history, published by the Remington Arms Company in 1944, "In Abundance and on Time, 1939-1943." "When conversion of small arms ammunition to steel was ugently desired by the Ordnance Department, Remington produced accepted cartridges in calibers .45, .30 and .50; also shot shells and experimental lots of caliber .22; also practically all types of bullet jackets. In all, more than 3-1/2 Billions rounds containing steel in place of brass were produced." (Page 28 of the above cited reference).
The Bridgeport works alone proced 259,178,335 shotshells during the period covered by the history. The Peters Kings Mills plant produced 125,400,235 shot shells. Remington even made clay bird targets (166,259,325) and Traps (5,996) for the Government at their Findlay factory.
The U.S.Army Air Force found teaching aerial gunners to trap shoot in their basic training made them show a big improvement in aerial gunnery when they went on to machine guns. After a study of reasons for the high degree of accuracy among American fighter pilots and bomber gunners, the British decided to introduce shotgun shooting at flying targets in their marksmanship training, during the summer of 1943.
Well, I got off on a tangent I guess. Shotguns in the Service make for an interesting story, not just with the guns, but also the ammunition and training. Of course, I am sure that some of the above ammunition by Remington was 00 Buck made for guard guns, as well as probably for the USMC that used shotguns heavily in the island fighting, proven by many combat pictures showing them with all manner of "Trench Guns."
John Moss Edited to correct a typo only