Good question, though a headspace issue is exactly what I'm trying to correct. I was just told by my smith today that I'm about .002" past the FIELD spec. For $45 I can get a NOS bolt from Liberty Tree, which is cheap enough for me to take a chance on that fixing my issue.
I am going to offer something that is almost 100% ignored by today's shooting society.
Chamber headspace is measured from the cartridge base to a location on the chamber shoulder. It is an important measurement.You can more or less see the relationship between case and chamber with this picture
If the cartridge headspace, that is base to shoulder measurement is too short, the shoulder will not be firmly supported in the chamber, misfires can happen. Also, if the case had to move an excessive amount to ignite, the front becomes fixed if the case and chamber are clean and dry, and as pressures build, the case sidewalls will stretch leading to case head separations. Like this:
But, the real importance of headspace is that it is a measurement that is easy to do by the user, and if headspace is excessive, the assumption is that the lugs or the receiver seats have set back, and cartridge case head protrusion is excessive. The shooting society basically ignores this because of all the emphasis on reloading, but this concept, how much case head is sticking out of the chamber, is the real safety critical aspect of headspace measurements.
These are case head protrusions in a Mauser barrel and a M1903 barrel
Chinn explains the importance of case head support in his series "The Machine Gun Vol IV". If too much of the case head sticks out of the chamber, the case ruptures:
The mechanism which Chinn shows has a lot of case movement before the case head is out of the chamber is the Oerlikon advanced primer ignition mechanism. And it worked because it used lubricated cases.
The base to shoulder distance of this mechanism is almost irrelevant and it increases after cartridge ignition. But, by the time the case head is out of the mechanism interior pressures have dropped to the level that the case head won't burst.
How this relates to your problem is,
maybe someone in the past stuck a chamber reamer in your rifle and excessively deepened the chamber without changing the case head protrusion. If this is true, reloading for this action will be a bother, but firing cartridges is not necessarily dangerous.
Have you fired any cartridges in this action and where is the pressure ring on the case head?
I am going to say, with 30-06 based cartridges, any case head protrusion 0.2" or more is going to guarantee a blown case head. The web of the case will be outside of the chamber.
Most case head protrusion measurements I have seen are just around 0.1", half of 0.2". I have seen 0.105" for some actions. I think the Mauser is less. If the case head protrusion on your rifle is just at 0.1" inches, and not even close to 0.2", than I am going to claim, you can fire cartridges in your rifle as long as they are lubricated.
I don't have a good way to exactly measure this, but I think determining how much case web is inside the chamber, based on the pressure ring on the outside of the case, is one way to estimate case head protrusion.
Case lubrication will allow the case to slide to the bolt face without excessive case wall stretch. Then, once fire formed, you can bump the shoulders back about 0.003" from fired, and use those cases in that rifle until the cases wear out.