RWS makes both BB (Ball Breech) and CB (Cone Breech) caps.
(Like the the little copper-colured cased version shown) ... the BB is a round
pellet, while the CB is pointed.
CCI makes both CB shorts and CB longs ...
Remington re-introduced their "CBee" 22LR - HP's a year or so ago,
and Winchester has the Super-X CB-Match. All are under 800 fps.
All the BB/CB's are very quiet, more so than the sub-sonic rounds, which on
average are about 300 fps faster, and the 22 shorts, faster still.
Of all the variations, IMHO, the RWS BBcaps are the quietest,
and least powerful - very limited penetration when compared
against the others. Also the most difficult to load. The CCI,
Remington & Winchester's all cycle pretty well through magazines,
but don't generate enough pressure/gas velocity to cycle semi-autos.
CCI - CB's will group into one ragged little hole at 25 yards out of a
Browning T-Bolt I have.
On a good day, you can actually watch the flight of a BB cap
projectile against an overcast sky.