I apologize for bumping an old thread, but I've found that my guns tend to like the CCI CB series better than the Super Colibris, I've also tried the Rem. CBees
In terms of power/noise/accuracy, from best to worst, they go; Rem. CBee, CCI CB, Super Colibri
I've dissected all three rounds to see what makes 'em go, the SC has a double-thick dose of primer, and nothing more, the CCI CB has the thicker primer, *AND* .5 grains of propellant, the Rem CBees have the thicker primer and .8 grains of propellant, both the CCI CB and the Rem CBee contain a small amount of "gunpowder"
the CBee's group the best in my guns, *BUT* have an unacceptably high FTFire ratio and the velocity is not consistent, some are louder (overcharged) and some are quieter (undercharged), out of my last box of 100, I had five cartridges that would just plain not go off, when triaged, they had the .8 grains of propellant in them, but no priming compound
the CCI CB series are more consistent, very few over or undercharges, they are also rather quiet, in a break barrel Sportster, the sound of the hammer falling and the *thwump* of the bullet hitting the target are louder than the sound of the round going off, I have also had 100% reliability from these rounds, and I've shot a few hundred of them, they don't hit as hard as the Rem. CBees, but they are more consistent and reliable
the Super Colibris, well, the nicest thing I can say about them are they're the quietest of the bunch, nearly silent, the hammer fall is the loudest noise the gun will make, accuracy-wise, I have yet to find a rifle that will get decent groups with them beyond 15-20 yards, that seems to be the max distance in my guns, accuracy is hit-or-miss, mostly miss, IME, I'd limit myself to no more than 15 yard shoots with these