If you ever come across the original CB caps, "Acorn" by RWS in Germany, grab them! A triangular bullet 15 grains in weight, IIRC, with a case shorter than our Short case. No powder, just the priming mixture. VERY quiet in a rifle bbl. I was able to group them in a rifle at 20 feet.

Pretty much anything will be noisier in a handgun bbl than in a rifle.

Kaaskop49
Shield #5103