Some have a dab of powder, some don't. The really short copper-cased CB and BB caps from Germany (RWS) don't. (The BB caps have a round shot for a bullet, the CB ones are, as might be expected, loaded with a conical ball.)
I accidentally killed an amorous dog once with one of the powderless RWS CB caps. Regretted it, since I only wanted to pelt him while he was sniffing/digging around my pheremone-filled kennel.
I consoled myself and assuaged my guilt by saying to myself, "Oh, well, if you let your dog run around uncontrolled, what can you expect?"
The CCI ones do have powder in them, at least the ones I've dissected. Apparently, CCI feels that since the priming charge is so inherently variable, they can "swamp" this variability by adding some powder --but this is just my theory.
The Aguila ("Super Colibri") ones don't.
I shot some of the Aguilas out of a well-used .22 Remington rifle. The first one got stuck in the bore, and I pushed it out (easily) with a rod and ran a bore brush through it. The others went through cleanly after that. One of the advantages of this bolt rifle is that it will feed shorts, longs, and long rifles from the magazine, so it was a lot of fun cranking the bolt and firing again. Grouping was not too bad, 2" or so in my 11 yard living room, but firing was done with a scope focused for 50-100 yards, and the image was therefore blurry.
These powderless Aguilas are, as described, very quiet, with the firing pin click being louder than the report in a rifle. They make a moderate bang out of a pistol. If you are in the room, there's no mistaking that a shot was fired.
They do dent the back of a Beeman pellet trap, so I stuck a 1/4" aluminum plate back there, once I plastered up the holes from my first misses. Stupidly lucky me there was no wiring back there under the drywall. They penetrate about 150-200 pages of a phone book.
The CCI ones (with the aforementioned dab of powder) do make a noticeable crack, even out of a rifle.
Sighting with the Aguilas is problematic. I found the Aguilas shot about two inches to the right compared to regular rounds at only 11 yards (living room distance) out of that Remington rifle.
Tried single-loading them in a tube-fed bolt rifle which wouldn't feed them out of the complicated lifting mechanism of a tubular magazine rifle, but this was awkwarder than hell, so quit it before substantial results could be reported.
Another thing you might try (outdoors + backstop!) is the Aguila SSS (so-called "Sniper Sub Sonic") rounds which are low velocity and loaded with a loooong 60-grain bullet in a .22 short case. Oddly, I found these to be pretty accurate out of a .22 Auto pistol, and they cycle the action pretty much normally, as would be expected with the heavier 60-gr bullet. However, the short case sometimes gets hung up on ejection. But they too are quieter than the regular .22LR --as was the design goal.
That's my experience.
Bear in mind these are not toy rounds, and can kill... as in my dog incident and the deer incident cited in a previous post.
