It is advertised as "600% harder than chrome-moly" and also advertises that it will restore accuracy to a worn bore and even out pitting or imperfections, also making a claim of 70% greater accuracy. It seems this product is aimed toward semi-auto rifles like M4 and M16 type rifles.
Seems too good to be true, I would also think of concerns with putting a layer of anything in the bore that would make it tighter, thus increasing pressures. If it does work, I wonder if it would have applications in bolt-action rifles.
I would not use it in any collectible rifles, it wouldn't seem "right" to put a ceramic bore coat in a 50+ year old classic battle rifle, but if it does work I would think about maybe using it in one of my commercial AR's, my AR-180b, and 1 or 2 of my "beater/shooter"uncollectible franken-bolt guns.