ME- I am not disputing what you have said (I don’t think) but I have read quite a lot on trench warfare for the Great War (my grand uncle participated in a few- I would have been scared as shit). However, I have never found or remember much of a mention of shotguns. They weren’t standard issue AFAIK so ammunition would have been difficult to obtain. I thought coshes, knives and pistols were more common on trench raids.
I know that the M1917 was an “issue” weapon (as per Ned Schwing’s The Winchester Pocket Guide in the period 1917-1918 and again during the Pacific War during WWII (I’ve seen photos of soldiers with them).
Also, my copy of “The Illustrated Book of Guns and Rifles (Edited by Frederick Wilkinson)” says on page 140:
The Americans had issued the Pump-Action Winchester Model 97 riot guns for guarding prisoners of war, but many found their way to the trenches via such unorthodox channels of supply as stud poker, horsetrading, and scrounging."
I know one of my reference books somewhere has mentioned British troops using sawn-off hunting shotguns in trench raids, and I’ve heard a couple of military historians here and in NZ mention ANZAC troops using them at Gallipoli, too.
So they weren’t widespread, but shotguns were used for trench warfare in WWI- certainly on the Allied side, at any rate.
That still doesn’t confirm to me that they were used in trench raids (hey- we aren’t going to have a barney). The Americans may have issued them but they didn’t join the conflict until 1917 and didn’t arrive in real numbers until a little later. They were very successful in their actions- at a cost of course- but to what extent they were involved in trench raids is a bit of a mystery.
And it doesn’t give much weight to British and ANZAC forces using shotguns.