Mystery Caliber

[don't]

Good Day,

Recently acquired a drilling I am having problems identifying the rifle caliber.
It is an Austrian Drilling marked Johann Perterlongo on one shotgun barrel and Tiroler Waffenfabrik on the other. It has the following letters under Crowns in various areas on the barrels S, U, W, G, N There is also 0/55g G.B.P over a line and under the line is STMG. The shotgun barrels have a 16 in a circle and 16/1, they are both also stamped Nitro. The shotguns chambers are definately 2.5" (65mm) and choked Full and Full+. It is an internal hammer gun, dual triggers and the front trigger is a set trigger.

The gentleman I got it from has been shooting the gun with modified 32-20 rounds. They are necked down to 25 Caliber (6.5mm) using a 25-20 die. I slugged the bore and it is fact a .257" groove diameter. He has also used 25-20 shells as well. When first fired it moves the shoulder ahead on the 25-20 rounds to fire form the brass.

I did a chamber cast and it appears the dimensions are as follows:
Rim: .425
Case diameter right above the rim: .348
From base to the shoulder: 1.058
Diamerter at the shoulder: .348
The neck above the shoulder is .300 and tapers to .282 and is about .350 long.
Overall Cartridge length is about 1.46 inch

I realize the 25-20 and the 32-20 cases are about .25 short but they seem to work fine and I am getting decent groups using a 75 grain Hornady Jacketed bullet with 7 - 7.5 grains of Alliant 2400 powder.

With taper of the neck I am thinking this may be a long throat but it is hard to tell. I have pored over all my cartrige of the World books and Donnelly's cartridge conversion book for obsolete cartridges and nothing.

Any thoughts on what it might be and the best parent brass and dies to use. Like I said it is shooting OK with what I am using so far just thought I would see if anyone had any thoughts on what it is??

Thanks in advance for any help you can render..

Sincerely,
Don

[mike ford]

Don,
Your drilling does carry the name of an Austrian dealer, but seems to have been proofed,consequently made, in Germany. The proof marks are those usually seen on German guns. The "S" means it was intended for shot,the "W" means the barrel is choked(amount not specified),the "U"is for the "view"proof(a detailed inspection), the "G" means proof for a solid projectile(rifle barrel, whereas S is for shotgun barrels), The "N" is for nitro proof. If the word "nitro" is written in block letters, it was proofed in Suhl; if in script letters, it was proofed in Zella-Mehlis. It was likely made near where it was proofed.With these marks, it should also be marked to indicate the caliber. If before 1912, this would be a mark designating the guage of the rifle barrel's bore diameter(not groove).For this rifle,it could be marked 313.If you read it correctly, the 0/55 g GBP, over StMG, would be the proof load; 0.55 gram Rifle Flake Powder and a steel jacketed bullet. This does not seem to match the caliber, so it would be good to verify the numbers.
From the information you provided, the caliber might be 6.5x41R Tesching, known in Austria as 6.6x43R Hirtenberg, introduced in 1908 in Austria. As always, I might be wrong about this, but if I'm correct; 6x70R Norma/6x70R Krieghoff would be the easiest brass to use. I would first try to "swage" the head of 5.6x50R brass, since I would be hard pressed to shorten 70mm cases that much. I came to the conclusion that this is the caliber because 25/20 cases are 34mm, you said they are about .25"short, which would be about 6.4mm. This would add up to 40.4mm. Considering the way I arrived at this length, it seems pretty likely to be close to correct. If Axel will weigh in,he might have another idea. BTW, what you are doing now seems to be pretty useful,but I can see that better fitting cases would be more satisfactory. I believe Huntington Die specialities have or have had 6x70R cases, as well as 5.6x50R. Buffalo Arms may have 6.5x41R cases already formed, but I didn't check. If so, I believe you can buy one case to check.
It would be helpful to have photographs.
Mike

[Axel E]

As you describe a bottlenecked cartridge wit a base diameter of about .348" and a length of about 41-43 mm, both the 6.5x 40R G Tesching, straight taper and 10.2mm = .402" base, and the .25-20 Single Shot aka 6.5x41R, base .315" are out.
As the drilling was obviously made for sale in Austria, this leaves us with the Austrian 6.5x 43R Roth, G.Roth case number 775. Sorry, but load data are unknown to me, but the drilling was proofed for a smokeless load and a steel jacketed bullet before 1912. Apparently the cartridge was obsolete quite early, as the 1927 Georg Roth cartridge catalog does not list it any more, though the .25-20 SS is still featured. Early Austrian smokeless chambers, f.i. 8x50R Mannlicher, quite often had no distinctive step from neck to forcing cone, but just a constant taper from shoulder to rifling, making actual case length less critical.

[don't]

Mike and Axel, thanks for the reply help is appreciated. here are some pics of the gun & barrel flats. Again thank you for your time. Don

Pics:

[mike ford]

don't,
The photos show the word nitro written in block letters, this indicates it was proofed in Suhl, therefore I believe it was made there.Also I was surprised to see the caliber marked in mm, since you hadn't mentioned it. I now believe the drilling was made a little later than I said before. The 1891 proof law was "improved" in 1911, which improvements were finalized in 1912. The main improvements were changing from guage measurement of bore diameter to mm measurement, case length was also shown after the improvements were implemented.Because your drilling has the mm bore diameter but not case length,I believe it was made during the transition time, or late 1911 to early 1912. BTY 6.2mm bore diameter is common for rifles with 6.5mm groove/bullet diameter. For whatever it's worth,the drilling looks nice, I expect you will enjoy it a lot.
The cartridge I IDed and the one Axel did are the same, even though the numbers look different- they have the same Roth case number.
Mike