I know that jug choking can be an effective way of providing some choke to a cylinder bore shotgun, provided that there is sufficient barrel wall thickness available to remove enough material to create a section of choke boring. But considering that 70% is considered Full choke, and 73% is considered to be Extra Full choke with lead shot loads, I think a claim of 80% patterns sounds just a bit optimistic.
Of course, in the early days of Choke Boring, a lot of wild claims were made by various gunmakers in their advertising. All the same Stan, I know you will enjoy having Vol. 1 of the excellent Gunsmith Kinks series, and I'm equally sure you would enjoy having Volumes 3 and 4 as well.
