My recollection is older Brownings and I think Winchesters, an improved cylinder was only .006 constriction.
Roger
Roger, your recollection is accurate on Winchesters. Per Jack O'Connor's "Shotgun Book", the Winchester standard constriction for 12ga IC was .007. But the old Belgian Brownings were at the other end of the scale: .013, again per the chart in O'Connor's book. And that agrees with what I've found measuring Belgian Brownings: they're typically choked a lot tighter than you would expect, based on the choke markings on the gun.
