I once had an old-type Ithaca Deerslayer with 20" smoothbore barrel. I had a Weaver J-2.5 scope on it, and found one lot of Remington Foster-type 1-OZ slugs that would group into 3" @ 100 yards. matter of fact, I still have maybe five or so of those slugs, although the gun itself is long gone!

I would start off by zeroing it in dead-on at 100 yards. To accomodate what that Lightfield article says, (which I think is at least half horse-feathers!!) do it on a windless day or on a day when the wind is travelling straight up or downrange.

Even if you had 6" of wind drift at 100 yards, and zeroed to compensate for that, you'd still have LESS than half that amount of "bad" windage cranked into your scope at 50 yards; probably no more than 2" at the most!(I really wonder about what someof these 'experts" write.)

Then I'd shoot it at 50, 75, and 125 yards to see how high it is closer than100 yards, and how much it drops from 100 to 125. At this time, I would also check to see if the windage is off, as alleged in that Lightfield article, and if so, by how much! Then hold accordingly at the various distances ......