Where have they all gone?
Try Beaufort's **** or the Hurd Deep:
http://www.mod.uk/NR/rdonlyres/5750E...y_sea_dump.pdf
When I was first finding out about Rosses about 12 years ago, one of the Ross experts told me that a lot of surplus weapons that couldn't be off-loaded any other way after WW1 were simply dumped at sea - along with the worn-out Smellies, knackered artillery pieces - oh! and lots of unused gas projectiles and other obsolete high explosive . . .
This is why the UK was in such desperate straits in 1940-1, after the BEF had lost the majority of its equipment at Dunkirk and the arms factories and US contractors weren't yet up to speed - there was no reserve at all to fall back on.
And in 1946-7 and onwards to the 1970s, the same thing happened again - especially as Rosses, Arisakas , P14s and P17s, etc were now considered obsolete when matched against AK47s and so on . . .
Try the diving clubs/websites - most have them have stories of wrecks of military transports and evidence of dumping of all sorts of military material - it's just that simple rifles tend to get forgotten in the fuss about obsolete and deteriorating NBC weaponry.
Sorry, but I can't remember my source - I think it was one of the Canadian experts, but I'm not sure about that.
As for Rosses in large numbers in Russia - surely they would have been in the first convoys to Russia in 1941-2, and so issued to the PBI fighting the 1942 summer campaign, Stalingrad, etc and then Kursk? Some of those would have been captured by the Germans and would have appeared long since, especially with the collapse of the Warsaw Pact and the selling-off of obsolete military hardware to all comers? And we would be seeing Rosses with all sorts of non-British/Canadian (i.e., Cyrillic) stamps?
P.S. Sorry - this website won't let me enter the word **** - hope my meaning's obviious with a little bit of Googling