A dent like that or any dents are not that hard to fix....if you are handy. The first thing is you have to know bore size.
This is what I do, measure bore, then I make aluminum plug gages a thousandth under size of the bore. These are 1" long and threaded 1/4-20 on one end. The opposite end has a slight bevel. I fasten this onto a 1/4" dowel that has a threaded male and slide it into the barrel, hopefully it goes to the dent. If not I make another one two thousandths under and try that. If that works I make a steel plug 4" long that has a 3/8-16 thread to the size of the aluminum plug. The length of the straight part is around 2-2 1/4". I use some oil in or on the plug and slide it into the bore. I lightly heat the area with a propane torch so that it warm to the touch, slide the plug into the dent area and ether tap it by hand or tap the end with a mallet lightly until I feel the plug going under the dent. Once the plug is into the straight part most of the time the dent is out, but on one like yours you might have to massage the barrel lightly with a brass or hard plastic mallet. Most of the time you can barely see where it was and does not discolor it.
These are for a 12 gauge.
Steel plug for 10 gauge.
Dent in 10 gauge.
Dent removed.
