This will probably get multiple opinions- here's mine-
The degree of accuracy sought with that product and process would be discernable to a long range benchrest shooter that is trying to shrink a group from .39 to .30. Sorta like putting a turbo on a Yugo for a lot of folks.
I have seen several products used for fire lapping. Some swear by it, some swear at it. Some barrels may need it more than others. I do have a couple of older target rifles with hand lapped barrels- and they all shoot better than I can.
Would this give you OMG accuracy out of a Mini-14? Doubt it. Could it improve the accuracy of a 6mm BR rifle? Possibly.
Used to know a guy that ran a "Speed Shop"- place that sold aftermarket stuff to go on a car when you were building a racer. Had a sign that said "Speed is expensive. How fast did you want to go?" Same thing applies to accuracy.