Jani:
First, let's deal with this one:
But 6.5x52R (as made by Norma, RWS, S&B) and .25-35 Winchester are one and the same thing, which is confirmed by all standard references starting from Cartridges of the World.
God, no. I don't know how you've gotten so mixed up, but you're badly misinformed. I assume that you're actually referring to physical dimensions, which are indeed close. I'm not surprised that a .25/.35 cartridge will fit in your rifle, and that's unfortunate. The 6.5X52R and .25/.35 Winchester are NOT the same cartridge and are NOT interchangeable, nor does anyone intend them to be. The assumption that they "are one and the same thing" IS dangerous.
From your description of the markings, it certainly sounds like your rifle is a 6.5X52R. Unless the maker actually marked it ".25/.35" somewhere, it isn't a .25/.35.
CIP specifications for both are here:
http://www.intermin.fi/intermin/images.nsf/files/B0E765375DA00143C2256FBE0032DD2A/$file/TABIIcal.pdfFor ease of review, just print pages 12 and 58. As you can see, dimensions are very close, but certainly not identical, and it's clear that they're not intended to be interchangeable.
The fatal difference is in the standard pressures. CIP Max Average Pressure (pmax) for the 6.5X52R is 2,450 BAR/35,534 PSI. CIP mandates that official proof ammunition produce a mean pressure of 125% of MAP (pmax X 125% = PE: proof pressure). Thus, CIP proof ammunition for 6.5X52R must produce 3,060 BAR/44,382 PSI. A new rifle must survive only two of these bombs to pass proof. CIP pmax - Maximum Average Pressure for STANDARD AMMUNITION - for .25/.35 Winchester is 3,050 BAR/44,236 PSI. CIP standard .25/.35 ammunition is PROOF AMMUNITION when fired in a 6.5X52R! Especially since yours is a drop-down barrel action, that would be a grave error, and unequivocally unsafe.
Perhaps you understood this, but it sounded like you didn't, so I thought it best to clarify the difference. Now, to your original question.
Gentlemen:
My Rasch combination gun (Büchsflinte) from the 1920s is chambered for .25-35 Winchester (besides 16g), which in Europe is usualy named 6,5x52R. But this one is marked 6,2mm/52 on the barrel flat. Why is that? My guess is this is land diameter of the rifled bore, or maybe bore diameter before rifling, but would need a confirmation. The reason is I have trouble registering this gun as the caliber on invoice (6,5mm) is different from the marking on the barrel flat (6,2mm).
With kind regards,
Jani
I'm surprised you're having that problem in Europe, as there are so many European rifles floating around from those days with caliber designations in the proof marks that don't match the nomenclature of the round. Yes, in those days, the 6.2mm referred to bore (land) diameter, not groove. The difference between the two is usually about .012", or rifling .006" deep. For example, "6.5mm" (.256" bullet), marked "6.2mm" (.244" bore) = .012" of diameter is rifling. Think of all the 8X57J rifles marked "7.8mmX57" at the proof house - .318" bullet vs .307" (7.8mm) bore = .011". The S bores at the time were marked "7.92mm" - .323 bullet vs .311 (7.92mm) bore = .012". The 9.3X74R rifles were marked "9mm" at the proof house (.366" bullet vs .354" (9mm) bore = .012". This is nothing if not common. I would have assumed that your authorities would be familiar with it.
I'd suggest getting in contact with the proof house in Hannover - maybe your G. L. Rasch was proved there since it's the closest one to Braunschweig. At any rate, if you send them photos of the proofs, they should be able to explain the matter to the satisfaction of your authorities.
Good luck.
