"they should be actually measured"
They were Don - bores for both left the factory (but may have been altered) 17mm or .669"
16g bore for British and U.S. guns usually .662-.665
Zoli
16.2 = .638 = .031" constriction = light full
16.0 = .630 = .039" = really full
Laurona
16.4 = .646 = .023" = improved modified
15.9 = .626 = .043" = crazy full
But what matters is the performance on paper or birds; either a 30" circle at 40 yds (25 yds for skeet) or the distance at which you anticipate shooting game (sea ducks at 50 yds or woodcock at 15 yds
)
