Duggaboy,

I remember now - these data come from an article by Svein Sollie, published in Norway.
I got an English translation of the text from a collector and handloader in Norway.
Here is the part referring to cartridge and reloading. Plenty of good information, and it fits to the loads that I worked out - will descibe these in a separate post.

Fuhrmann

ENGLISH EXPRESS CALIBRE
The rifle barrel is chambered for the .260 2 1/4'' Express, an old English black powder cartridge that especially in German speaking countries survived the transition to smokeless powder. It was in German speaking countries usually called 9.3x57R, after its calibre and length of case. Since there is no rim version of the Mauser cartridge 9.3x57, there is little reason for confusion, but surprisingly many think of the bottle shaped moose cartridge when they hear the name of the cartridge. In contradiction to that one, we are talking about a slightly conical straightwalled case, charged with a considerably lighter load and bullet than we today associate with a moose cartridge.

The .360 did in its time make basis for a whole family of rimcased calibres for use in cape guns and drillings, with case lengths from 48 to 82 mm. The most famous of these is the 9.3x72R which is the only on of them has survived up to our days. As one might know, this cartridge is loaded with a 12.5 gram (193 grain) softpoint bullet loaded to a muzzle velocity of about 600 m/s, and is known as a very capable roe buck cartridge. The original ballistics for 9.3x57R was a bit more moderate, around 400 m/s with the same bullet, but at its height of popularity, it was charged with smokeless powder, giving speeds close to 500 m/s.

There was also a 8x57R/360 - which was the 9.3x57R/360 necked down to a bottle shaped case and loaded with an 8mm bullet. The "/360" was of course necessary to differentiate this calibre from the more well known - ordinary - 8x57R. There were also other small calibre cartridges based on the .360 case, for instance 6.5x48R, 6.5x58R, 7x72R, 8x58R and 8x72R. The well known contest cartridge 8.15 x 46R was also based on the .360 case.

The Englishmen loaded .360 2 1/2'' with bullets form 155 to around 190 grains, usually paper patched bullets with hollow point and round nose. The oldest loads were of the "coiled express" type, meaning cases that were made by rolling coils of copper, much the same way they did for the Snider and Martini Henry rifles. These were soon to be replaces by drawn copper cases, which of course was much better. The load was 50 grain black powder, regardless of bullet weight.

Smokeless loads, ''nitro for black'' loads were also launched after a while. The calibre must not be mistaken for the .360 Nitro Express though, which used the same case but was loaded with a 300 grain jacketed bullet at a much higher pressure.

Unfortunately there are some differences between British and German arms in the .360 / 9.3x57R calibre. The rifling diameter for English weapons could be as small as .358'' (9.09mm), while the German guns usually measure in the range .364 - .366 (around 9.3mm). That makes differences in the wall thickness of the brass, where the English usually measures 0.25mm while the German measures 9.35 across the neck. There are also variations both when it comes to rim thickness and base diameter, and old German catalogues differ between "Englischer Form" and "Deutscher Form". There is even a "Norwegische Form" made for Larsen and Hagen, who also disagreed with everyone else on what a .360 case looked like. Gunsmith Larsen in Drammen did by the way chamber his pistonrifles for what looks mostly like the English version of .360 and charged it with paper patched bullets.

Husqvarna on the other hand stuck with the German measurements, and the barrel of my Model 17 measures exactly 9.3mm, and has a seat that fits the 9.3x72R head precisely.

LOADING THE .360
I had plans to use the Husqvarna for occasional hunting, and set the goal to load cartridges for the rifle barrel. By trimming RWS 9,3x72R brass down to correct dimensions, I got perfect cases, and I found loading tools for the same cartridges could be used for the shorter 9.3x57R. Calibration was sufficient, the expander die worked satisfactory, and the bullet seater also worked well when I turned off a bit of the threaded part of the die so that the case entered further into the die.

Lyman is the most economical source for this die set, and ''Parabellum'' got me mine. The shellholder is of course the same as for 9,3x57R.

It looks like 9,3x72R now goes out of RWS sortiment, but "Parabellum" has got cases from Sellier & Bellot instead. They also claim that ready 9.3x57R cases can be bought from the American company called Ballard Rifle & Cartridge Co.

There are also base cases to be bought from Australian "Bertram", and also Olav Heidenstrøm got me an amount of .360 cases. My "Bertram" brass was of uneven quality in this calibre though. They had to be carefully calibrated with a minimum of grease to get the correct
conical shape without dents, and then be trimmed to correct length. The head/rim is thinner than their German counterpieces, since "Bertram" has used the old English dimensions. The case weight is also varied, some cases significantly lighter and more thin walled than others. This caused some of them to crack. Some of them also had the primer pocket out of center, but after a session of sorting I had a nice pile of brass at my hand.

BULLETS
Since I to be on the safe side in the beginning decided to use only blackpowder loads in the shotgun barrel, it was natural for me to concentrate on blackpowder also in the rifle barrel. I god hold of a "Jämtången" bullet mould, that cast a 200grain round nosed lead bullet with shallow grease cannelures. These bullets measure about 9.3mm right out of the mould. Later I talked Jan Marman in Drøbak to make me a mould for a 190 grain flatnosed bullet, with deeper cannelures to hold more grease. This is of course crucial when shooting black powder.

Most shooters of vintage guns are well known that the black powder loads should be compressed, in the sense that no air must be present in the case between the powder charge and the bullet. At the same time, it is practical to leave space in the case for a cardboard pad and one or two thin slices of grease or wax. In the .360 case, a load of 45-46 grains of GoEx FFg gave muzzle velocity of around 1400 ft/sec in the Husqvarna, depending on bullet weight and primer, which is about 425 m/s. This corresponds well with the original data, even though the thinwalled brass yields space for more powder.

The precision with these two bullets was approximately equal, around 5cm on 50m range, and with correct point of impact. I have also tried loading with Hodgdon's Pyrodex RS instead of black powder. This powder is loaded using the same VOLUME as the black powder load it
replaces, and since Pyrodex is much lighter and more fluffy than black powder the load reduces to around 31 grain to give about the same or a little higher muzzle velocity. I could not find any precision difference between FFg and RS but Pyrodex fouls less and is a usable alternative. Loading techniques and requirements to the greasing is the same as for ordinary black powder.

The Husqvarna has two rear sights leaves and a trapezoid front sight. With the lowest sight, the point of impact fits well at 50m, but at 100m the bullets fall pretty much, whole the way down to the edge of the cardboard of the animal target figure I was shooting at. With the highest leaf my gun shot a bit high at 100m, an easy thing to adjust.

SMOKELESS LOADS
The 9.,3x57R was also loaded with jacketed bullets and smokeless powder. I got hold of some Sellier & Bellot 193 grain bullets for 9.3x72R from "Parabellum". These bullets are nearly identical to the RWS bullets, with a very thin mantle, and semiwadcutter profile. Such bullets are made for lead bullet barrels by the German gunsmith Collath at about the time when one converted from black powder to smokeless powder, and often shoot very well in old guns.

This was also the case in mine. I found that Vihtavourii N120 was a suitable gunpowder, and loaded charges of 19 to 22 grains using the S&B bullets. With the hottest load I got 515 m/s, about 5cm above aimpoint on 50m. On 100m it fell around 15cm with the same sights - in other words a very reasonable roe buck load. Precision was also better than the black powder charges. After my calculations, this load holds 1016 Joule at 100m, against the 736 Joule for the black powder load. In other words - this load qualifies the requirements for legal roe buck hunting.

I must of course make myself some reservations against recommending smokeless charges in old guns, even if barrel wall thickness and the calibre’s history implies that smokeless charges were used also back when the guns were new. The safest is probably to find a load that corresponds to the black powder load and stop there. Around 19-20 grain N120 should be suitable. I chose to increase the load a bit in order to find something that corresponded to the old smokeless loads, making the cartridge legal for hunting. 22 grains of N120 gives a somewhat higher pressure than a full case of FFg black powder, and since the firing pins of these guns are pretty big, the primers have a tendency to develop craters. I am not scared to use these loads in my own rifle, but I cannot without further notice advice others to do the same. It is up to you what you choose.