8x50R Type 45: Adopted in 1902 (2445) it is a 237 gr., .321-inch diameter cupro-nickel clad, full metal jacket, round nosed bullet. Approx. Muzzle
Velocity: 2050 fps.
The cartridge case was made of brass with a Berdan primer and on the bottom of the cartridge case it is marked with the numbers 45 in Siamese script. Only ball bullets were used. This cartridge was made in both Japan and at the National Arsenal in Bangkok.
Note: The Siamese Type 45 is not interchangeable with the Austrian 8x50Rmm cartridge even though that round was used as a basis for the development of the Siamese Type 45 cartridge.
In the early 1920's the Siamese wanted to upgrade the Type 45 cartridge to a more powerful and pointed type of round for use in their Browning F.N., Vickers and Madsen Machine Guns and the Type 45 was not suitable for this, thus they developed the 8x52Rmm Siamese Type 66 cartridge.
The 8x52Rmm Siamese Type 66 cartridge was adopted in 1923 (2466), using a spitzer boat-tail bullet, lead cored, a gilding-metal or copper-washed steel jacket design that weighed 181 grains and had a diameter of .323-inch with a muzzle velocity of 2250 fps. The cartridge case was made of brass with a Berdan and later Boxer primer and on the bottom of the cartridge case it is marked with the numbers 66 in Siamese script. Ammunition was also made in Tracer, Armor Piercing (AP) and Armor Piercing Incendiary (API). This cartridge was made at the National Arsenal in Bangkok until 1953, Japan, England (Kynoch), Denmark and Finland (Sako).
When the Type 66 cartridge was adopted, most 1903 Siamese Mausers were re-chambered and/or re-barreled to handle this cartridge. When the weapons were converted the rear sight base was cut down to give the correct elevation with the new ballistics of the Type 66 flatter trajectory, thus taking off some of the original sight graduations. This is the easiest way to tell that the weapon has been converted to the new round. It was also common practice for Japanese Arsenals to put a second assembly number on rifles that had to be rebuilt, thus you can find some of these converted weapons with two assembly number and Katakana symbols. This second assembly number is placed on the bottom of the receiver just above the original assembly assigned number. If the conversion took place at the National Armory in Bangkok it lacks the second assembly number. On some of weapons the trigger guard is usually marked with a 66 indicating that the magazine box has been converted to accept the longer Type 66 round and other parts of the weapon might also bear the 66 markings. It has been debated if the barrels on these conversions are re-chambered or re-barreled as most of the time the barrels look like they are newer to the weapon itself as the rear sight bases on them are usually pitted and the barrels are not.
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