Gunman, that explanation sounds good . . . but it runs afoul of British proof laws and what is marked on the guns. If that were true, ALL barrels on ALL British shotguns would be marked "choke", because they would have passed proof with more than .008 constriction. In fact, a lot of British shotguns are not marked "choke", especially in the right barrel, because that barrel is quite often more open than .008--and was more open than .008 when it was submitted for proof.