Re: Mauser Rifle Serial Number Identification
Savage Doherty
When Siam contracted the second batch of 20,000 rifles (serial numbers 20,001-40,000) there were some slight changes made to the design.* These changes were made due to the Japanese-sourced wood having an inherent weakness that could lead to the stock splitting. Despite these changes, the rifles were still designated as the R.S. 121 like the previous batch and marked as such. When Siam moved to the new calendar however they decided to apply a new designation to the rifles with these changes to denote that these rifles have differences from the original Type 45 pattern. The designation Type 46 however applies to more than just the rifles from this second contract. As Type 45 rifles were damaged it was common to rebuild them to the newer Type 46 pattern, so they too are designated as Type 46 rifles.
The Type 46 rifles had 4 main differences between them and the Type 45. To deal with the weaker nature of the wood available in Japan, they changed from a stock made from a single piece of wood to one made from two pieces like those found on the Japanese Arisakas.
Along with the two-piece stock, they also added an upper-rear tang off the end of the receiver and a lower tang off of the trigger guard (both of which required a very minor modification of the original design), again very similar to what is found on the Japanese Arisakas.
Along with a new rifle Siam adopted, it also adopted a new cartridge. This new cartridge, like the rifle, was also originally designated as the R.S. 121. This later was redesignated as the Type 45 after Siam moved to the new calendar like the Type 45 Rifle. This cartridge is an 8x50mm rimmed round with an approximately 239 gr. bullet that fired with a velocity of approximately 2050 fps.
With the introduction of a newer cartridge, Siam began modifying the Type 47 rifles for use with the new cartridge. This involved two main changes: reaming out the chamber slightly so the new cartridge could be chambered and grinding down the rear sight ramp to match the ballistic trajectory of the new round.
* Typical of contracts such as this the supplier often assembles slightly more rifles than called for as it uses up all of the parts manufactured to construct the rifles. Thus, the high serial number reported for Siamese Mausers is 40155)