I'm wondering if there is much sound coming from the action opening as with a 10/22 or by the time the action opens and the case is removed has all of the sound already passed away from the gun?

I don't think there is much sound coming out of the breach end of a semi-auto, particularly a .22. Yes, there is a mechanical noise while cycling and whatever noise brass makes when it hits the ground, but a decent suppressor on a .22 will quiets things down considerably.

The gases escaping the ejection port of a .22LR are very slow, and do not cause any audible 'pop'.

As Matt said, there is the sound of the bolt cycling, which can be eliminated by using CCI Quiet loads.

George

You can also block bolt by thumb (.22 LR only). It will give you a little kick, but nothing bad at all. Tried many times on a Ruger Charger pistol and some russians .22 LR.