Many years ago, I shot BB Caps (ball bullet, primer load only, no powder). They were really inexpensive and great fun. I had a bolt-action Marlin and they worked really well. I think I shot CBee Caps, too. Are they also primer-only, no powder?
CCI makes CB shorts, and longs. Remington makes(made?) the CBee LR. All have powder charges, but are virtually silent out of a rifle. Aguilla makes a colibri round that is primer only, I believe.