Let's look at that Epps video a little closer.
The Epps measurements were .692" at the choke and .818" at the bore's widest point for a .126" difference. The standard constriction of a tight 12 gauge full choke is .040" while the tightest turkey choke I could find is .060" meaning the choke on the Epps shotgun is over twice the constriction of the tightest choke on the market.
The question it raises for me is how long the Epps gunsmith spent reaming that barrel. A .818" bore is larger than a 10 gauge and is closer to an 8 gauge. Yeah, sure it came from the factory that way. :rolleye: