Feasibility of opening up a choke / Browning Model 12 20 gauge

whatnickname said:

The OD of the barrel is .707”. The ID dimension is .696”. That gives us a thickness of .011”.

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No, that gives a wall thickness of .0055". You have to take half the difference in OD and ID because there are two sides. And ther is no guarantee that the barrel walls are equal thickness all the way round. The bore is often not concentric with the OD. That said I find it hard to believe that the barrel walls are even as thin as .011". Are you sure you read the calipers correctly?

.011" is the thickness of a spent .22 LR case neck.