Jager: there is no concern about the slight rise in pressure using standard 2 3/4" shells in a 16g M97.
The problem is that 2 3/4" shells will often hang up in the ejection port, which will need to be modified.
OTOH nominally 2 3/4" modern 16g shells are often shorter than 2 3/4". The old black Rem. Game Loads were, but not anymore. Aquila 1 oz. were reported to be short, but components change.

Winchester Super-X 16g 1 oz 1165 fps in 2023 67 mm

[Linked Image from photos.smugmug.com]

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