OK. I'll give this one last shot,then you can call it anything you want.
As I already suggested,search "headspace" and review what has already been discussed. The dead horse has been beaten down to a flat greasy spot.
I'm not interested in an ego based whizzing contest. I was gently,respectfully trying to educate you on a fine,but importsnt point.
Your 30-30 was designed the headspace on the rim.The headspace gauges,GO and NO GO, will represent the high and low limit for the breech face to the rim recess. You can cut the chamber properly or check headspace withoutnhavng a round of ammo within 100 miles. Headspace is entirely within the gun and its about building the gun to a standard.
Not all guns headspace on the rim.Some headspace on the shoulder,some on a belt,and some on the case mouth.
In each of those systems,we are taking about the feature that controls how far the cartridge can move forward off of the breech face.
The headspace dimension is from the breech face to whatever chamber feature limits the case forward travel If you choose to use the shoulder,thats fine. You probably won't have a SAAMI correct headspace gauge. That's OK.
As the gun isn't going to change,you are concerned with handloading the ammo to freely load and lock,yet you want to minimize case stretch. All good. You are using a feeler gauge to check HEAD CLEARANCE,not headspace. You are doing it so you can tune your sizng die to optimize your AMMUNITION. Headspace is purely n the gun and has nothing to do with ammunition.
Now,once again, I only mentioned the terminology to help you out.
In post#12,I quote Reynolds
I know what happens when a rifle is fired.
You might want to educate yourself on a Contender. Please "educate" me on how I misunderstand your Contender. I am sure it will go something like "The primer ignites the powder. The primer is slightly pushed rearward before the pressure fully expands the brass and in the process of completely filling the chamber re-seats the primer." You must tell me how you have a headspace of .003. That will indeed be an education. Saami minimum is .063.
Reynolds had you there. It was apparent you did not have the terminology quite down. That's why I tried to help you out.
Its not personal,and I don't want to play whizzing contest.You may take it or leave it.