You are off on both counts, but it's because of your gun.
The CB's arent great in a semi, because even though they wont cycle the action, they do open it enough for some gas to escape.....this is the "bang" you are hearing. Also, because it's a low velocity round, the energy wasted opening that action just a bit lowers your velocity. CB's out of my 22" barreled pump will go right through a phone book.
Next time you are shooting them out of your 10/22, hold the action closed with your thumb...it will be much quieter.