I'm not even sure specifically which rapidfire it is, but over the months I've seen a new "Awesomer faster lee7ers amazinger" rapidfire come out ever week, and ever week there is a customer who swears it's faster and there is another customer who says it doesn't work at all lol. The fastest in my mind is still just the standard rapidfire macros from the library. I've tried everything and I haven't found a way to cheat the speed cap. I think customers dial in like 16 SPS and if it shoots at all they claim success and say they have fast rapidfire at 30SPS when in reality if you watch it in a video it's still just shooting at 7-8 SPS. It's realy hard to explain why some rapidfire macros will still work when "overdialed". Typically if you dial in "multiples" of the max speed... for example if the cap is 7.2 sps, then typically 14.4 and even 21.6 sps will also appear to work. Hard to explain the phenomena in the forums without charts and graphs lol. It basically has to do with sampling frequencies, aliasing, and even temperature variation affect on DAC's and even manufacturing tolerances in Microsofts controllers.
The moral of the story is on the COD games rapidfire works best down around the 6-12 SPS range depending on the gun and anything faster ain't gonna work.