I don't think a comparison of a couple of VL&D exports/imports and a German inland is fair as well as mixing bores 12, 16 & 20. It's not comparing apples to apples. Of course the probability of a 70mm chamber in a U.S. of A. slated gun is high while that of a German inland is high for the 65mm chambers. I'm not sure when the 16X70mm came into being but I do know that many of the the early Belgian A5s were 65mm. But I can't say on the Winchester Model 1897. So for the period in question, 1912-1923, when smokeless was coming into its own, in 16 bore the 65mm was King on the continent(someone feel free to grace us with a set of proofmarks with a 16 bore with 70mm chambers from the period). If it wasn't a 70mm then the default was 65mm. Regarding the inland, 70mm stamp was typically below the calibre stamp and the cartridge had to reach the appropriate pressure. The rule was for it to be on the tube & chamber but some are seen on the extractor. By 1939 there were 2 choices regarding proof for the 16 bore, 65 and 70mm. For cartridges with a length longer than 70mm, for every 5mm there had to be add an additional 1470 psi increase. True strictly pulling out the encircled 16 would just note a bore. But the proofmarks are more of an ensemble and tell the tale. The 1st Imperial Eagle with the encircled 16 being devoid of a "70mm" stamp and a "Nitro" will note that black powder proof only for a 65mm chamber. The addition of "Eagle Nitro" and "Eagle Nitro" & "70mm" changes the tale.
Kind Regards,
Raimey
rse
