WOW... some of you guys really shouldn't chime in if you don't know the answer... there is some questionable info in the above posts. I'll try to clear this up a little.
Ok, for starters, the M96 action is just the rifle length version of the M94 carbine action, which itself is a nearly exact copy of the Spanish M93 action as designed by Paul Mauser in 1893 (!). The only real differences are the serrated safety flag on the Swedish action and the elevated thum tab on the cocking piece. Mechanically they are identical. (Reference: The Mauser Rifle in Sweden, Dana Jones)
The M98 action was a further development of the M93 action. The differences are many, but in essence the primary differences are:
- addition of the third locking lug at the rear of the bolt (safety lug)
- Bolt shroud now retained by a spring-loaded plunger (M93 is just threaded on)
- Extractor guide groove cut further back on the bolt body to prevent wear and breakage of the extractor guide rib
- Shape and size of gas vent holes changed.
- The M98 is #### on OPENING, though the sear is only reset against the cocking piece on closing. All early Mausers #### completely on closing like a Lee Enfield.
- The M98 bolt shroud was enlarged to better deflect gas from ruptured cases away from the shooter.
- The action was switched from a small ring design to a large ring design, mostly to add a factor of safety for higher pressure cartridges back when Mausers were only carburized and case hardened.
(Reference: Mauser Military Rifles of the World, 4th ed and Back Bone of the Whermacht, 2nd ed)
Other differences, obviously, center around the stock design, the band arrangements and the sights, etc. But the primary mechanical differences are outlined above.