I do not have any published data but do have three Parkers with letters that specify choke, 60660 8ga O grade letter says RH 115 #4 pellets in a 30" circle at 40 yards LH same. The chokes measure .025/.026. 157318 PH 8ga specifies in the letter RH modified, LH full and the chokes measure .038/.042. 161252 GH 8ga specifies in the letter to pattern with BB shot RH full, LH full. The chokes measure .046/.045.
It seems to me from a very limited sample that the restrictions are the same you would encounter in 12 and 10ga guns.
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