The 640s were built on 2 different actions, "strengthened" commercial pre-1898 style small ring Swedish actions and large ring 98 actions made by FN. The "strengthening" involved the elimination of the thumb slot in the left receiver rail. I have a few 640 in 6.5x55 and 8x57 built on both actions. I converted the SRs to cock on opening with the Dayton-Traister kit and replaced the triggers with Timney units. The LRs feel and function like any other commercial Mauser 98.
The 1600/HVA series action is basically an in-house hybrid of the 2 actions that Husqvarna had used in the 640 series.
All of my rifles with HVA actions have mannlicher-style full length stocks and were purchase because I like most rifles with mannlicher-style full length stocks, not because of the actions that they are built on. For me, the Husqvarna mannlichers have the best balance of any regular production rifle with a mannlicher-style stock, making them a good choice for still-hunting. It seems that people either really like or really dislike mannlicher-style stocks, sometimes to the point of obsession.
If you want to go getting technical, the 640 series was built on 4 different actions: The so called "strengthened" action, an FN Supplied Military pattern action, FN Supplied transitional commercial action, and the FN Commercial we are all familiar with.
