The classic stainless has a 24" barrel in standard calibers, the Ext Wx has a 22" fluted barrel.
The classic has a MIM extractor, the Ext weather has one of spring steel.
The classic has 2-piece steel bottom metal, the ext wx has a one piece unit.
The classic has the original open trigger, the Ext wx has an enclosed box style trigger, both great triggers imo with a preference to the old style for simplicity and ruggedness.
The extreme wx has fiberglass stock that is quite stiff, the clasic stainless has a injection molded stock.
The ext wx has a aluminum mag follower, some of the classic stainless have a synthetic follower.
Owned and hunted with both for many years, both very good. If choosing today, Id opt for the Ext wx for better stock.
