I shot both the K and S at a Hunter match last year. The S is quieter with more recoil. The K is louder with less recoil.
I have the K. The recoil is on par with a Kelbly's brake. It's substantially less than the UL7. I'd say the noise is near hearing safe. I'd have no issue taking a few shots without ears. I'll use it for hunting.
I used a decibel meter on a phone to test sound reduction. No doubt the numbers are not accurate but should be comparable. The K reduced sound by 20 db (at my ear on the table) compared to the Kelbly's brake.
I haven't yet compared recoil to my DN5 or Without Warning brakes.
I have shot a couple of the RR cans.
I found them to be pleasant to shoot on magnum 30 cals. (300 RUm, and 30 Sherman)
I can't say on noise reduction, other than significantly better that the breaks on same gun prior to.
Shot 25 Saum today running a 'magnus K-RR and a 25 creed with TI PRO 4 side by side. I'm extremely impressed. Much quieter as expected but I'd say the perceived recoil was equal or lower then the 25 creed. In reality recoil was probably very close but seemed less due to the almost non existent concussion at shooter. Very impressed. And ordered another one lol