Sorry I may have got my terminology wrong, I have just looked through the CZ manual that was linked earlier in the thread. look on page 24 in the reciever (not the chamber) just above where the stock line finishes inline with the forward edge of the magazine. There is a small hole which I was told in the gun shop was a lubrication hole.
I understand your comments but this is behind the breech when the bolt is closed and I was advised by the gun shop that this was the purpose of the hole. It is not a gas vent as this is covered when the bolt is home.
Sorry I am new here and I did not mean to create offense.