Hey Ed. As I understand "invisible" rifling, it is very shallow, every wide rounded grooves (have heard only 2) and lands with a quite slow twist, making it difficult to easily discern. Looking the length of the tubes, should show an impression of the interior twisting.
I tried to have Hugh Toenjes make me just such a barrel for shooting round balls, reasonably snug patched however at that time and now as well, he believes nothing more shallow than about .028" depth will work in ANY rifling with patched round balls.
Lanvaster's invisible rifling was meant for the short paradox'type bullets.

As far as I know, it worked well enough for close-range dangerous game killing/stopping.