After thinking about it for while, there is a difference in some of the calibers I think. I have owned an SKS and a AK47, both 7.62X39's. Plus a 30-06 and an 8mm mauser. Both the larger guns where louder if I remember corectly. I remember shooting the AK for the first time and commenting that I though it would be louder. The action makes more noise than anything, still it gives off a pretty good report. And If I remember correctly the .223 wasn't quite the same as the AK or SKS. I don't know if there is a decibal difference or not, but you can for sure tell the diffence between an AK and a AR/M-16 when they are fired. As far as bolt actions go, I couldn't tell you.

I know my inline muzzle loader is louder, you can feel it when one is fired.

I think any of the centerfires would be fairly louder than a 17hmr. It sounds about like a .22 mag rifle. More of a loud POP than a BANG really. Of course I may be half deaf as well.

Paul