As expected, more great SOLID stuff, Wayne. Knowledge hard earned, as it were, and it's GREAT that you are passing it on.
I'm just going to toss in a few parallel observations, re: longer straight cases, primer protrusion, and "Case Stretching".
A.) A rifle set up for the woods and hunting fields, particularly one dedicated towards collecting those that shoot back should be granted a certain dispensation, in terms of headspacing. Reliable chambering and extraction should trump precision just a skosh, perhaps ?
A dedicated competition rifle on the other hand should have it's rim recces depth determined by the average aggregate rim thickness of the brass chosen, and THIS should be determined before the chamber is cut. Given that one will be buying the stuff by the HUNDREDS, it's never a bad idea to order in a hundred extra, sit down with a Mic, and discard those cases with overly thick, or thin rims. SAAMI specs are all OVER the place when it comes to our old "Obsolete" cartridges, and some of the headspace callouts seen on recent ( say the last 60 years) drawings are just stupid sloppy.
Good uniform rim thickness dims give us an unparalleled "Accuracy Edge" that is just not available with rimless cartridges, and it's a shame not to take full advantage of that.
That said, I must sadly state that overly deep rim reccesses abound, and that some of the sloppier "High end of SAAMI specs" examples were cut in Italy.
B.) An important nail was hit squarely and hard when you stated that internal case cleanliness will go a long way towards slaying the stretching bug-bear, as WELL as pulling SDs and ES's into a tighter band......BDDT.
Thank you for your continued contributions to the compendium of BP lore, Amigo !
GTC
