The whole idea, is that a larger diameter, almost bore size ball can be loaded with a thinner patch, say .015"patch for example, yet fill the grooves & give good accuracy yet load easily and allow heavier loads for flatter trajectories over hunting ranges and not build fouling shot to shot. That's a tall bill.
This type of rifling might have a definite use in areas that have to use non-lead balls. Due to being non-compressible, these balls literally cry out for shallow rifling so that the patch can provide the fit and spin to the ball, where the ball's circumference in not 'disturbed' by the lands. The rifling will have to be slow, to allow the shallow grooves and high velocity with good accuracy. The shallow grooves also allow the thinner patch for easier loading.
The idea, of course, was developed/designed by Lt. James Forsyth in the mid 1800's. Today, we and our modern barrel makers are still re-learning what was proven to be 'best' way back then. Forsyth-style rifling was designed for large bore hunting rifles, to produce the highest speeds for flattest trajectories with them, when at that time, the normal gun maker's push was for faster and faster twists which they thought made guns shoot harder - black magic/voodoo or whatever - it's BS.
Thankfully, a 'forward thinking' person, namely Forsyth though out and brought forth the truth in the matter and actually published it so we could re-learn as well. How it will work in small bores, I'm not positive, but it shows promise under some circumstances.
The reason for this type of rifling is quite simple. In Forsyth's day, barrel makers were running twists in large bore rifles, 16 through 10 as fast as 2 or 3feet. These fast twists would not allow heavy charges needed to kill dangerous game without the ball and patch stipping. Accuracy suffered and of course, the trajectories with the light loads make hitting problamatice and the wounding of game, the norm.
The slow, shallow rifling of Forsyth's design allowed easy loading, heavy charges and the accuracy actually improved the more powder was used. A man's capability to handle recoil was the only block to the amount of powder used - large bores - remember that.
Today, in our .50's, .54's, .58's and .62's, with their 60" to 80" twists, we can use the heaviest powder charges they can use that allow flat shooting loads and top velocities with great accuracy. They too, give better accuracy with the higher speeds we give the ball. Forsyth rifling may or may not help in these guns - but.
That style of rifling will allow looser fitting loads to be used - that's a plus for those with small wrist diameters, but it won't allow more powder than can already be used. Today's normal twists are almost slow enough to be Forsyth-style and allow about all the powder than can be utilized.
The difference is some gun makers today still think deeper is better, when that's the wrong direction to go from a hunting rifle standpoint. Yeah - rounded deep rifling easily until they foul out for most people, then they have to wipe - to the point they think everyone must do the same. A tight combination like Taylor uses in his .016" rounded rifling Rice barrels, doesn't foul, doesn't build up fouling and it is as easy or easier to load the 50th than the first. THAT's a nugget - pure gold, but it's a tighter combination than some people can load, it seems. With deep grooves, more of the ball's mass must be moved by the lands if accuracy is a requisit.
Hopefully, the same caliber with Fosyth-style rifling will allow the same or similar accuracy, same clean shooting chacteristics but with loading that can be accomplished by someone who has difficulty with current barrels.
For them, or someone who has to use ITX-type balls, this form of rifling might be a hobby saver.