Because pattern welded barrels were overbuilt to compensate for fools like this.
1917 Damascus 10g Ideal “Waterfowl Special” (
NO SUCH THING) with 3 1/2” chamber
http://www.doublegunshop.com/forums/...=420838&page=1
The gun was offered for sale again in 2016 - “My brothers shotgun, he has had it approx 2 years. And fired it 50 plus times with factory smokeless 3.5” Magnums, shot a turkey with it this spring!”
The crolle pattern is obvious under the blueing on close examination.