With reference to the Peabody-Martini converted to 7.65X53, I had one of these rifles several years ago. It was in almost un-used condition since conversion. The dealer I bought it from did not even know what calibre it was. At the time, I didn't either and bought it for $99.00 and took it home to do some research (Before the internet!). I first suspected that it might be in .303 Britishicon, 8mm Mauser or 7.65 Turkishicon. I had a pretty extensive military arms collection at the time and had about 13 different rifles cartridges at my disposal. I tried the first two and then the Turkish round slid right in. A trip to the range confirmed it. It was actually a fun little rifle to shoot. I sold it several years later, still without really knowing a whole lot about it (Still before the internet). It was only much later that it came to light. It recognized who had done the conversion from the markings on the back of the tangent rear sight leaf, but at the time, that was about it. After some research on the web, here is what I have found...

Turkish 7.65mm Peabody-Martini Rifle (M71/74 Apt.)

Already in 1891/1892, Oberst H. v. Lobell mentioned in his annual military publications about changes and advances in the military world , that the available Peabody-Martini rifles according to proposals by Paul Mauser , should be improved by fitting a 7.65mm barrel, in order to require only 1 single cartridge. However, only 20 years later were Paul Mausers ideas executed, which meant that the Turkish conversion program started at a moment that the British one had already been finished for quite some time. From October 1910 till March 1911 (Turkish financial year 1326), the Turkish military purchase office ordered from the Osterreichischen Waffen-Fabrik Gesellschaft in Steyr 150,000 barrels in calibre 7.65mm, 150,000 rear sights Model 1903, 25,000 forends including hand guards Model 1903 for the Transformed Martini-rifle in calibre 7.65mm. These entries can be found in the contract book of OEWG, page 130, numbers 1 to 4.
Delivery time was stated as 18 months as from payment of the 1st instalment. Which means we can reasonably assume that the Government Rifle factory started with the modification of the old Peabody-Martini actions as from 1912.

Description
1. Barrel (similar to 7.65mm rifle M.1903)
Calibre: 7.65mm
Barrel length: 740mm
No. Grooves: 4
Groove depth: 0.125mm
Width of grooves: 4.20mm
Twist: 250mm
Direction of twist: Right
At the muzzle, the new barrels were dimensioned to use the old Peabody-Martini bayonets.

2. Sights and hand guard
(Similar to 7.65mm rifle M.1903), with rear sight graduated from 200 up to 2,000 M.

3. Block
The large loading groove was retained, and the block was slightly shortened, so as to allow the fork-like extractor/ejector, now with insert for extracting the small rimless 7.65mm cartridge, to be positioned unhindered in front of the block.

4. A new forend (maintaining the old fittings) completes the fittings. Length of the converted rifles is 114 cm.

The left side of the receiver of the converted rifles now has, in addition to the markings Providence Tool Cy., the arsenal nomenclature Istanbul in old-Turkish, and the year of conversion 1912 (Turkish financial year 1327).
The Martini action in those days was could still be found everywhere. A conversion of these rifles to a modern, small-calibre cartridge could lengthen its useful time span. OEWG-Steyr found this niche in the market, modified the Martini extractor for use with a rimless cartridge and patented this modification in 1892. It is quite probable that the news, already made public in 1891, that the Turkish empire would convert its 600,000 Peabody-Martini rifles to the calibre of the Mauser M.90 rifles, played quite an important role in this decision.
The operation was very simple. When opening the action, the front of the block pushes on the lever part of the extractor (P), which moves the extractor, and engages the groove of the cartridge case. A further push on the lever takes care of the extraction of the empty case.
This is most certainly not a simple modification, a completely new extractor had to be made. This conversion presumably was too expensive for the Turkish military, and they chose a cheaper variant, modifying the existing extractor with an insert the Austrian construction was not adopted.

Mauser 7.65mm cartridge

OAL: 78mm
Weight: 27.6g
Case length: 53.6mm
Case weight: 11.6g
Bullet length: 30.8mm
Bullet weight: 13.7g
Powder charge: 2.65g
Powder type: Rottweil Bl.88/91
Max. Pressure: 3000 bar
Bullet type: Nickel-plated, steel-jacketed bullet with lead core.
The conversion program would only be completed during WWI, as the pattern room of Royal Ordnance, MOD, in Nottingham has a rifle only converted in 1915 and it is possible that there are rifles with even later conversion dates.

Conclusion

The marriage of the old, but robust Martini system with a modern, state-of-the-art cartridge can be considered as a success. In the 1st Balkan wars, WWI and the conflicts shortly hereafter the rifles was used with complete satisfaction. Although it didnt have the speed of fire of the Mauser rifles, it was most certainly their equal as to precision and reliability. As from 1933, with the general introduction of the 7.9mm Mauser cartridge in the Turkish army, the M.71/74 was taken out of service. There is no record of a new calibre change. Hereby I do thank Wolfgang Seel and Herb Woodend for their help and patience!

Heino Hintermacher

Sources:
Edward A. Hull: Providence tool Co. Military arms, USAicon. 1978, Santa Rosa printing 531 W. Elva St. Milton, Florida 32570, USA.
Herb Woodend: Catalogue of the Enfield pattern room, Royal Ordnance, MOD, Nottingham, UK.
Oberst Heinrich von Lobell: annual notices about changes and advances in the military, Berlin (editions 1878, 1891, 1892) from the records of the University library Salzburg, Austriaicon.
Wolfgang Seel: Mauser rifles under the Half Moon/Turkish Mausers, Deutsche Waffen Journal, Verlag Schwend GmbH, Schwbisch Hall.
Contract book of the OEWG (1869 1913), records of Steyr-Mannlicher GmbH, Steyr, Upper Austria.