Fooled and Fooled Again by Shotgun Bore Diameters

“In the absence of contradictory data, collected and analyzed with the care

used here, it is reasonable to conclude that good guns are insensitive to their

bore diameters in the range of 0.724" to 0.745" and the near-universal move

by manufacturers from the classic dimensions to the modern ones has not

improved the patterns produced by their guns at all.”

“This result is consistent with Dr. Jones’ conclusion on page 153 of Sporting

Shotgun Performance: “The story of over sized (Back-Bored in this case)

barrels is no story. The onus is on the proponents of Back-Bored guns to

produce robust evidence in support of their claims. I think it is unlikely that

any will be forthcoming.” Neil Winston

It is one of things that has been going on for many decades, with no end in sight. The unsubstantiated, unproven claim of “back-boring” or using larger than standard bore diameters continues. Yet, there is no scientific evidence to back up the claims of improved pattern efficiencies and no shareable data from the manufacturers and other entities that publish those claims. But, even though there is nothing to show that a larger than standard bore diameter does anything beneficial for patterns, it persists. There was no discernible pattern efficiency increase with my Stan Baker “MoneyMaker” 303 barrels from years ago and nothing has changed in that regard today.

Yet, tell a fairy tale loud enough and long enough, sometimes it gets blindly accepted as fact. That has been the case with bore diameters to an unprecedented extent. The Browning brand has been the most effective at it, for Browning more than any other manufacturer has made a larger than standard bore sound beneficial. So much so, that due to the acceptance of the baseless notion that a bit larger bore somehow helps things, Beretta and many other nameplates were forced into oversize bores one way or another. The door swings both ways, for Benelli has their standard bore called the “Power Bore,” but swings things back to slightly over-sized bores for the pricey “Performance Shop” branded guns.

This isn't to suggest that shotguns with larger than standard bores don't go bang and spew pellets, of course they do. There is no verifiable or shareable evidence to date that shows they do anything at all that improves patterns, though.

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