Hello GRF,
The Husqvarna 1640/1600 action and Husqvarna/Carl Gustaf 1900 action do use the same bases. I am pretty sure the military Swedish Mauser uses the same as well. The Weaver 46 and 55 bases are the correct bases for the 1900 and 1640 actions. I have had Weaver 25 and 35 bases on 1640 actions as well, and they will work. I have seen other Husqvarnas equipped with the 25 and 35 combo too. The Warne M898/M828 bases for small ring Swedish Mauser actions are what I use a lot. They are the equivalent of Weaver 46 and 55 bases. Hope this helps out.
Best of luck,
sixfive
