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FWIW, even today's "light loads" are waaay too strong for guns like those, even if the guns are in primo condition.
That includes modern so-called "low brass", "target" & "game" loads.
One reason is that in 1926, long after those guns were made, all shotshell companies seriously upgraded ammo to different powders with higher pressures - more than the older designs could safely fire.
Even companies that made top-drawer guns, like Ithaca, discontinued their then-current models in 1925 (the Flues) and introduced a stronger model (the N.I.D.) because of the ammo issue with weak actions.
A second reason is the the metals used in Belgian shotguns 100+ years ago is in no way comparible to the modern steels found in guns today - besides who knows how much & what sort of stress that metal's been subjected to in that time ?
I'm sure there's more than a few who'll say they've successfully fired modern ammo in theirs - but I (for one) wouldn't want any such gun in my hands, near my face, when (not "if") it does finally fail.
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