I am slightly in two minds about Kynoch/ Kynamco. A friend shot some (modern Kynoch) 9.5 Mannlicher, all of which suffered case splitting (presumably due to insufficient annealing). On the other hand, standard calibres - .375H&H, .470NE - seem to be fine.
That's one possible conclusion and I'm not saying you're wrong. The other scenario is that the original chambers (and ammo) were looser than current SIP specs.
I've had this issue with 318WR. The original, 100 year old Kynoch ammo worked fine. New brass to CIP/SAAMI specs did not. Solution: new brass, do not full length size it, bump the neck back .002", let it headspace on the neck. The shot-out rifle with metford rifling ended up being a 1MOA gun.
I realize people have a man-crush on SAAMI and CIP but I use their docs for tissue. I only care about the Birmingham/London proof houses and the 100 year old ammo that was made to work in guns with chamber reamers of that era.
Some of you find it odd that I buy old, old Kynoch ammo all the time on this forum. I use it. The first thing I do with an old gun is shoot 100 year old ammo in it. Kynoch was so good, 99%+ of the time, they do fire and do so accurately. I then inspect the original brass fired from an immaculately clean chamber and bore. I then measure that brass post-firing. That tells me the story, usually that I must ignore SAAMI and CIP and use new brass with minimum shoulder bump to have a very accurate weapon.
Your new Kynoch ammo by law is sized to CIP specs, not to the specs that the original 100 year old Kynoch was made to. It forces your hand to load from new brass, or pull bullets and powder and fireform their new brass first.
