Shotguns in Europe at the time, at least to my understanding, were fowling pieces - usually single or double barrel break opens, used by "gentlemen".
Thanks, that was what I was trying to figure out.
Hadn't heard about the uproar that one Australian officer using his shotgun at Gallipoli, but that goes a ways towards explaining why none of the European powers used them as well.
So from this, and the other stuff that's been said in the thread, would it be fair to say that the European armies in WW1 never thought of using shotguns in the trenches for the following reasons:
- Any sort of shotgun would have been a special purpose weapon, only really useful for close-quarters fighting such as would occur when someone's storming a trench, and a rifle or MG would be more versatile and generally useful.
- The sort of high-capacity repeating shotguns such as the M1897 weren't all that common in Europe, with most being those break-action fowling pieces, which would have been less useful and such weapons would have been what European officers thought of when someone mentioned 'shotgun'
- It sounds like it wasn't just the Germans, but most of the armies in Europe who thought that shotguns, were at the very least playing dirty, if not highly suspect (or outright illegal) under their interpretations of the laws of war, regardless of whether buckshot would actually violate the relevant part of the Hague Conventions (or whether it would be any worse on that score than a lot of the other stuff in common use.)
If one's looking for a way to get the events of the OP to happen, perhaps you could have more British and French influence over the AEF, and the British and French high commands, seeing the shotguns and the US stance on them as likely to lead to a spiral of atrocities, somehow overruling Pershing on the issue and forcing the AEF to stop using shotguns in combat. Of course, with Pershing's insistence on a measure of independence for the AEF and hostility towards allowing foreign commanders to controlling US troops, one might need someone else in charge of the AEF to pull that off...