The fact that there is a 'bulge' no matter how much or little means that the barrel steel has undergone 'inelastic' deformation as opposed to 'elastic deformation'. Steel can and does undergo elastic deformation and returns to original dimensions with it proerties of tensile strength unchanged.
When steel undergoes inelastic deformation, the tensile strenght decreases and may fail subsequently catastrophically.-Dick
With all due respect, I disagree completely with the statement that "When steel undergoes inelastic deformation, the tensile strenght decreases and may fail subsequently catastrophically."
First, steels that are of low hardness like barrels, can be "cold worked" ("inelastic deformation" or commonly known as plastic deformation) safely and in most cases this enhances hardness and strength, and often increases fatigue strength. Heck, we do plastic deformation of parts specifically to enhance strength properties on airplanes all the time.
Dents as well as bulges are examples of plastic deformation. Both are safely fix by cold forming almost routinely, because barrel steels are very mallable. So mallable in fact, that the manufacturers routinely roll mark barrels, another form of plastic deformation.
So, I believe the notion that a little ol' .001" bulge reduces strength or is dangerous, is not only false in my estimation, but outlandish as well to this engineer.
