By late 1914, the Austro-Hungarian empire had already amassed thousands of captured M91 Russian Mosin-Nagant rifles, and began the work of converting them to fire the Austro-Hungarian M93 8x50R cartridge. There were two types of conversions done (this rifle is a Type 1 conversion):
Type 1 Conversion:
Lengthen the chamber throat to accept the longer 8x50R projectile. This was necessary because an 8x50R cartridge cannot fully chamber in a standard Mosin-Nagant
Re-cut the rifling to accept the wider 8x50R projectile. This was around a 0.323" projectile, vs ~0.310" for a 7.62x54R projectile
Type 2 Conversion:
Only the chamber was adjusted, the rifling was not modified. The Type 2 conversion is also referred to as the "Squeezebore" conversion
The conversion was done at several locations:
OEWG Steyr
Barendorf Arsenal
The easiest way to identify one of these conversions is by looking at the sight base. The sight graduations were renumbered to the Austrian "Schritt" measurement, with the numbers "6 5 4 3 2". These numbers were inlaid with a gold paint
It is not known exactly how many of these conversions were done, but it is currently estimated between 200,000 to 300,000 rifles were converted between 1915 and 1918. Most of these were M91 rifles, but some Dragoon and Cossack rifles were converted as well. After the Great War had ended and the Austro-Hungarian empire split apart, these rifles ended up in the hands of various new countries, such as Austria, Poland, Hungary, and Czechoslovakia. In the 1920s and 1930s, Finland purchased most of these already antiquated rifles, where they were either scrapped for parts, or re-barreled back to 7.62x54r. It is rumored that the chambers of some of these squeezebores were converted back to 7.62x54r, but more research is required in this area. Only a handful of these rifles still exist today in 8x50r, with a few more still waiting to be discovered in someone's attic in Europe
