Otto,
I'm sorry we haven't been able to find a quick and easy answer to your problem.Early 8,15x46Rs are sometimes like early 9.3x72Rs,in having problems with ignition,brought about by the first primers used in these cartridges.They were both made,in the begining, with 6.45mm(.254")Berdan primers,M71.This primer had a softer cup than we use now,and the larger diameter primer is easier to dent than the .210" primer we use today( I understand the M71 primer was developed because of problems with misfires in the Mod 1871 Mauser).Since you have been in the game a while,you may have some of the old cases in your "junk box" to try.The 6.45mm Berdan primers may be a little problematic, if you don't already have some.Both RWS and Alcan had them, not too many years ago.I suggest you try the best pin you have with the large Berdan primer, to see how it works. I could mail you a couple old cases,but sending a few primers would lead to complications, so it would be better to find them locally.
Other than this, I guess,keep trying would be the only thing left to do.I agree that the overall length is limited to the length of the breechblock.Within this it seems the only things to vary would be the tip protrusion,the rear end protrusion, and spring tension. To quote the King of Siam, "Is a puzzlement".
Mike
