Joe,
I may have missed the question. The only thing I am sure of is when Briley makes a choke, it is in relation to the barrel bore. The berettas I have are .725/.726. The chokes are based on a .725 bore as a compromise. When I once requested chokes for a right barrel and a left barrel be exact they did so and marked the chokes for the barrel they were built for. Give Briley a call and talk to a Gary Springer. The gent knows his stuff and he may help with a better explanation.
Best,
Ron