Do not use 38 Super ammunition in a firearm chambered for the 9mm Largo.
If the firearm you are shooting is designated for the 9mm/38 (which is the 38 Auto, not the Super Auto) as some of the Spanish designations read, then using either (9mm Largo or 38 Auto) in your chamber without modifying the extractor can be done. If the firearm is designated 9mm Largo, Steyer, Bayard, Bergmann, Bergman-Bayard or 9x23mm then the extractor must be modified to take the 38 Super case.
I don't think it is just the extractor groove. The 38 Auto and Super Auto are semi-auto versions of the 38 Special and are semi-rimmed cartridges that wear a small rim (which was the cause for a lot of the inaccuracy of 38 Supers). All the european 9mms mentioned above are true semi-auto cartridges that are rimless with an extractor groove.
Now, the European 9mms, especially the longer ones (longer than the 9mm Luger or 9x19) are definitely not in the same power category as the 38 Super. The Super is a much hotter round. You might get away with shooting 38 Supers in 9mm Largo chambered guns for a while, but you are most likely going to wind up with a broken extractor or even a split chamber and the gun then becomes a boat anchor.
9x23mm brass is available from any number of sources. 9x23mm brass duplicates the overall case dimentions of the longer Eurpoean 9mms and can be reloaded to duplicate any of the European 9mm power levels.
I would not fiddle with the extractor on any 9mm Largo firearm but just purchase 9x23mm brass and reload in the proper power range - like 9mm Luger levels. HTH and JMTCW. Mikey.
