I picked up a 20 ga., 30" Flues this year that I am quite fond of. One of the previous owners had the forcing cones elongated. A chamber casting told me that he did not ream out the chambers to 2 3/4" but just made the forcing chambers longer with a shallow taper. A compromise I guess he thought would make the gun safe for modern ammo. It ended up with a cracked stock but is otherwise still tight a they come. Now restocked but still needing checkering, I shoot low pressure loads but they are not wimpy ones. If you reload you can find low(er) pressure loads that are very useful in the field.
If I had a Flues in any ga. I would not alter chambers as I don't think removing metal improves the strengthen of any gun. Cut shells down if needed, reload low pressure loads or buy them if need be, but match ammo to guns design and your intended use.
