Good question and one for which it pays to have the correct answer.
A friend had a pump with plug in place, but for some reason the plug was a tad short, allowing in one extra shell.
Bob did lots of trading, so who know why or where this had happened.
Well he went hunting and sure enough a fish an game feller happened along and wanted to check the shotgun for legality.
Oooooooops, cost my friend!
On top of that, he knew of the situation BEFORE he was checked and just let it go.
Years back, but as I recall the game man ask Bob to load the gun, and had Bob just quickly fed in two to the magizine, an immeadiately pumped a shell into the chamber and then fed in the third shell to the magazine he might have ??? been Ok - that time -, but he just fed in three shells into the magazine without thinking and it cost him.
Didn't make that mistake again.
Keep em coming!
Crusty Deary Ol'Coot