Dean,
I don't know how you regulate/ enforce the rules. But those guns are out there and being used. Ask Pete Lester. He had to compete against a very good shooter using a British 10 ga rechambered to 12 ga.( I am sorry I cannot find his thread. He mentions the gun and shooter with respect and no complaints. I am using this as a reference that the guns are out there in vintage shoots)
there are several shooters who are in favor of this type of "modification". Look up Cyril Adams. Many trap shooters are having custom 12 ga guns made with 775 bores.
I am curious to see the opinions out there on this. I have considered a project for myself involving a 20 ga hammer gun. But before spending big bucks want to see how it would be perceived, as you say, be in good form or not. (I like the way you stated that BTW
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