Not sure of the question, are you asking about the face of the chamber? I assume you mean the extractor notch? ...or the overall profile? You can get measurements from here (and my site) about the default measurements of the diameters. You obviously need the barrel to fit the parts.
If you're talking about the extractor notch, you need to machine clearance for it during the entire rotation of the locking action. On an AKM/AK74 type of bolt, you're talking about 90 degrees from top-dead-center to about the 3 o'clock position when looking from the chamber toward the muzzle.
On an AK-100/AK-74 style bolt, you need it to be about 180 degrees around, from about 10 o'clock to the 4 o'clock location. By my measurements that was approximately .030" deep cut. Considering this is 9mm you should not be too terribly worried if it is a little deeper, however too deep and you'll expose part of the cartridge wall.
That is documented on my AKSU template at the bottom of this page - note this is for the short barrel AKSU, not a 16" barrel, so the overall barrel measurements probably won't work for your need. However, if you have an AK-74 style bolt, the chamber area should look like this: