Frank,  I measured my HORNET bolt face recess and it measures 0.356″, the same as in Lou’s  post.  To follow up on his post about the shell  being able to be held firmly in his example, and to his point that some HORNETS were converted to .222 Remington, if this is the case with your rifle, a simple test would be to insert a .222/.223 case head on to the bolt face to see if fits the recess .with the extractor rotated to 12 o’clock.  If it fits nicely with few thousandths clearance, then it has been modified.

 Likewise take a HORNET case and do the same procedure and see if the rim floats around.   With the case held firm to one side there would be a gap of about 0.025″ if modified .  If the gap is around 0.006″ you should have a HORNET  bolt.  This dimension would be larger if your case rims were at the minimum diameter.  This is possible and you did state that some cases are more problematic. 

In a short article by Robert Miller and posted by Dearcy Echols titled “CLAW EXTRACTORS 101”, therein states for ideal case tension  the  extractor should have a deflection of 0.004 to 0.005″ from the rest position to case insertion.  It went on to say that there is a lot of case head variation, in their example the were using 300 Winchester magnum cases, in measuring the extractor groove, it was found that a variation between different manufactures of 0.017″ which would make ideal extractor deflection and case tension problematic. 

I don’t have a HORNET extractor on hand for measurements for comparison to yours, so no help here. (actually I am looking for a HORNET extractor and you might have a spare, modified or not).

Hope this helps….

…JMc