Re: Belted Magnums--Headspace on Shoulder or Belt?
It would depend upon what headspace you had at the belt.
IOW a belted magnum might have .005" headspace on a new case which is the dimension between the front of the belt and the recess in the chamber it will bear against. But that same case may have .020" between the new case shoulder and the chamber shoulder. Then after firing you would have to push the shoulder back .006" or more to have it headspace on the belt again.
But if your chamber has a headspace of .001" which, again, is the distance from the front of the belt to the recess in the chamber against which the belt will stop forward movement, then after firing you would only have to push the shoulder back .002" to have the belt again act as the headspacing agent.
Now all of this will vary with different makes of brass and chambers.
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