First Generation Short Actions:
The 1st Generation short actions are often incorrectly referred to as "Series J" actions. These actions will have a three digit model number (110, 112, etc), but are approximately 0.540" shorter than the standard long action.
Savage used series letters (i.e. Series J) solely to identify small changes to individual parts over the years. These series indications were only used to identify what parts to use on the rifle should it ever come back to the factory for repair or warranty service.
As such, it's common to find a long action marked as being a "Series J", and as such it's not a good idea to simply refer to the 1st Generation short actions as "J-Series" as the series has no bearing on the actual action length. Additionally, an action can be marked with a series letter other than "J" and still be one of these 1st Gen short actions.