I didn't see this DR myself yet, but I asked this man about bore dimention several times and every time he replied bore = .450, grooves .458. Well. I guess it's 450 for real.
Then I asked about some 'shoulders' on chamber cast alluding to 500/450 case, but the owner is sure there is no any shoulders on case, it's straight and tapered.
Previuosly he was sure it's 3 1/4 case and has bought 20 cases from US, but when he got these cases, he can't insert case in chamber in full. Aprx. 1/4" of case sticks out from chamber.
Is it possible brand new cases have to be formed again before using?
Ah, now it's clear. There were several German or Continental variations most of the early "Express" rounds from the 9,3x72R through the .450 and .500 Black Powder Expresses. Dixon's book mentioned above has about the best explanation of these, but basically the so-called "D" or Deutsche form of these cases had a slight double taper instead of being just straight-tapered, probably left over from the earlier days of coiled case shapes.
I've not been able to come up with a decent keyboard-based drawing of this case form, but imagine if you will the difference between the letter "i" being a straight case and an upside-down letter "Y" being the double tapered Deutsche form. The rim and head diameters are the same, but the "D" form has a 10mm or so section just ahead of the rim that tapers more quickly than the now standard "E" or English form.
When trying to fit a modern case in one of these older chambers with the double taper the usual difficulty is that the modern case will not quite go in all the way, usually stopping with 1/4 to 3/8 inch sticking out.
I have an 1879 vintage Lancaster double in .450 3-1/4" BPE with this problem and a friend (I see he has already posted above!) has a wonderful Springer with the same difficulty. I have also seen many, many Drillings and single shot rifles chambered in 9,3x72R with this kind of chamber. I even had a 9,3x72R chamber reamer made so I could "Normalise" some of theses oldies. The amount of metal removed from the chamber is very small and it can be done just by hand with the right reamer.
The other alternative is either to have dies made to match a chamber cast from that rifle and form modern brass to that early shape - or to do as noted in the post above and 'cobble' some cases to fit the chamber. Once you have formed them, you probably won't ever need dies again. This is the best option in my opinion and keeps the rifle original.
