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Originally Posted by Kenno
That shumltz about rare switch barrel rifles,in a springfield,SHAME!
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You need to read more.
A good friend of mine owns a 98 Mauser switch barrel in .30-06 and .35 Whelen that JIm Caudill put together for him. It works just fine. This is something that used to be a pretty common practice between the World Wars, and was a strategy for saving weight when using more than one caliber. I think it has also been more popular in some countries where owning a number of guns is discouraged or expensive. I'm not sure why it lost popularity here other than it is difficult to get top accuracy from a barrel that is only tightened with a hand wrench, but fair hunting accuracy is perfectly obtainable.
The chamber itself is in the barrel which contains the pressure just fine. When you tighten threads the normal way, the greatest load from the installation torque is in the last turn of the thread near the barrel shoulder. It diminishes with every subsequent turn because the greater length of steel to the shoulder stretches. This is usually called barrel draw. Kunhausen puts it at 0.004" for a standard torque spec. That draw, as Mr. Guffey points out, will cause some degree of distortion, but what it does not do is change headspace in a rimless cartridge appreciably. That's because the shoulder of the case inside the chamber is deeper in the barrel than the barrel shoulder so it is not being drawn back after the barrel shoulder contacts the front receiver ring, as Mr. Guffey also explained.
Hatcher's old experiment extending headspace in the Springfield out 0.050" with a special reamer showed it will not create a hazard for new brass. Whether or not unacceptable pressure ring thinning results in the brass that might render it unreloadable has to be checked, but, generally. it will headspace on the extractor hook and be just fine for reloading in that same chamber, only. Consider that fireforming Ackley Improved cases moves metal a lot. There is no inherent danger in it. Certainly the microscopic differences in headspace from hand tight vs. barrel vice tight are far less.