A ring bulge always stretches the meta, I personally do not believe that all dents do. I fact I think a great number do not.
I have mentioned several times abut the "Crack" in a parts Twist barrel H grade Lefever I acquired had. One side of the crack was inward & the other outward. My "theory" is the barrel was dented & made the crack, then subsequently fired & the unsupported side raised. I placed by dent plug under the crack, raised the inward side hammered down the outward side. Every thing fit so perfect-fully after repair one has too look"Extremely Close" to find where it is. NO metal appeared stretched on either side. This brrel was subsequently fired with factory loads of 3 1/4-1 1/8 & 3 3/4-1 1/4 loads as well as a hand load off 1 3/8 oz, DE unknown. It was fired remotely via ye ole Firestone proof facility. Nn of these lads opened the crack in the slightest, nor did any Soot appear at the spot.
I have repaired one bulge. This one was on an Ithaca semi-auto & was just behind the choke. It was caused y a known obstruction. I removed the vent rib & then removed the "Cutter" from a pie cutter (Not a little tubing cutter) & just rolled it back down. Last I heard from it was still going strong.
I am not a metallurgist either but one machine shop I worked in I made a lot of test specimens for the "Met Lab". This much I did learn from taking with those wh did the testing. When pulling a tensile specimen when the Elastic limit is reached the metal suddenly stretches. Upon release of the tension it will not "Spring back" to its original state. how ever as the test continues to its ultimate where the specimen is broken more pull force has to be applied than what "stretched" it beyond it elastic limit before further elongation takes place.
This says to me that the just stretched steel is now stronger than it was just prior to stretching.
Somewhat surprised Rocketman has not weighed in on this, this is in his field of expertise.
