All the gas blow back pistol running Airsoft gas or co2 make a bit of a pop plus the sound of it cycling. Most non blow back pistols gas or co2 are a bit naff bar a handfull of models. And not as interesting to use lacking all the action of the slide etc. Some can be very quiet if suppressed. I have a bit of a fondness for spring pistols old ones anyway. Because I'm old and it was what I grew up messing around with. Definitely quiet. But once again lack function of a gas blow, back bar some obscure old ones.