Jimmy;
Do you have the means of taking accurate wall measurements down the length of the bbl. "IF" it indeed has adequate wall thicknesss over the chamber & for at least 12" or beyond with the thiness being confined to the last 2"-3" inches near the muzzle, I would simply shoot it, especially if it is closer to the .020 than the .010. Also if you could mic the od prior to firing & then again after you could pick up if it began to swell, which would be more likely to happen than a split.
Many shotgun bbls actually enlarge as they near choke area with a thinner wall from around 18" to a little behind the choke area.
Many who are screaming with hysreria would likely be surprised at what some of the bbls measured around the 18" mark on guns they have shot for years.
