Scapa Flow, if you don't mind eluding a crapload of destroyers on the way in. There are some battleships there, check the community manual/hunting grounds for more info. Also, try the eastern coast of Britain, and sail north to south and back. You'll get reports of single merchants pretty much every day.
Mosin-Nagant: When out of ammo, it makes a great pike, war club, boat oar, tent pole or firewood