Nice bit of info. Yeah, the round could have been developed between 1900 & 1910 and may have paralled the Gründig version?
yes, amazing paralell to the 10,75x52 R Gründig, in any case a full power nitro cartridge you will find in a strong break action only. Harald wolf had told me that the Springer Double Rifle he had in his hands was made from Francotte. I dont had such a DR in my hands till now but with a little bit more time I can probably find the gentleman the custum ammo was made for.
started a research on nitroexpress once to learn more about this cartridge, someone may know ithttp://forums.nitroexpress.com/showflat.php?Cat=0&Number=147203&an=0&page=0#Post147203
"I've just miked the barrels and I'm getting just under 11mm at the bore and just under 12mm at the chamber end."
sounds more like a 11,15x52R LK to me, 11mm barrel diameter is small but we will see what sluging and chamber casting will show