A recent archeological dig on an old Finnish mansion estate surfaced a used brass rimfire shell that to my surprise was of much larger diameter than a .22, the largest (yet very small) rimfire cartridge in use today, right? As the shell was squished it was impossible to measure the caliber, but I’d estimate at least 8 mm, but less than 10 mm (the base was 11 mm diam.). The shell was thin and short and the base had a hammer dent on one edge similar to what my .22 single shot makes.
What might this .30ish" rimfire cartridge be? The find conditions don’t offer much help, as the layers were thoroughly mixed and the site has been continously used for far longer than mass-produced cartridges have been around. How recent is the last large-cal. rimfire ammo?
10,4 mm Infantry Rifle M/1871 Vetterli, “Grafton-rifle”: Swiss made (designed by Friedrich Vetterli) model 1869/71 bolt action rifle with 13-round tubular magazine using 10,4 mm x 38 rimfire ammunition. During Russo-Japanese war of 1904 - 1905 Japanese were covertly supporting Finnish independence movement and Russian revolutionaries. Largest operation of this support was weapons delivery paid by Japanese government and loaded to old steamship S/S John Grafton. The most important part of its cargo were Vetterli M/1869/71 rifles (15,560 of them). Most of the cargo never got totally to its designed destination, as ship sailed to stone near town of Pietarsaari, got stuck and had to be exploded (there were also plenty of dynamite among cargo). Russians managed to confiscate most of the rifles that local fishermen had tried to rescue from the ship wreck. Only small number of these rifles ended immediately up to hands of Finnish independence activists. In another successful attempt made year later, when activists succeeded smuggling 3,125 Vetterli-rifles to Finland. Later doing the Civil War large number of the rifles earlier confiscated by the Russian officials were recaptured. According the ship of the famous first failed smuggling attempt these rifles are also known as “Grafton-rifles” in Finland. During Finnish Civil War of 1918 small amounts of these rifles were used (mainly) by non-frontline troops of both sides. But already then their use was quite limited due to shortage of ammunition.
As the shell rim was exactly 11 mm in diameter, and easily 1 mm or more wider than the shell base (which is slightly thicker than the bullet), and the cartridge was nowhere near 38 mm in length, the Grafton doesn’t match.