Jim K. I agree the Astra was never intended to shoot a wide variety of 9mm/.38 ammo as many have alluded, however, the gun WILL shoot 9mm Bergmann/Bayard provided you could find some as 9mm Largo is nothing more than a Spanish synonym for the same cartridge.
As for the Astra 400s,,,
There are military guns and there are commercial guns.
Military guns are marked 9mm on the chamber.
Commercial guns are marked 9mm/.38 on the chamber.
Some imported to the USA by Stoeger were chamber marked .38 Super Power!,!
These Stoeger imports probably started the misconception that the guns could use .38 Super cartridges and likely resulted in many of the guns being wrecked beyond repair as the older Super .38 shells were loaded quite a bit hotter than most of todays offerings and the Stoeger marked guns are quite rare even though they were imported in fairly respectable numbers.
The first imports of commercial 9mm/.38 chamber marked guns likely started the belief that ANYTHING with 9mm or .38 on the packaging could be stuffed into and fired from these guns and I'm sure gun salesman of the day were quick to point out this wonder of wonder as a quick and final selling point!
Cor-Bon .38 Super is likely about as close to the original loads as you can get today.
Don't shoot these in any 9mm Largo pistol regardless of the maker or the markings!
Do not confuse 9mm marked Astra 400s with the shorter Astra 600 which was chambered for the 9mm Parabellum.
As an added bonus, some Astra 400 pistols were rebarrelled to take 9mm Parabellum cartridges.
These can also be marked 9mm, or 9mmP, or 9mm Luger depending on who made the barrel.
If you compare the breechfaces of the two models you will note the commercial guns are modified and safe to shoot with commercial .38 ACP cartridges as well as 9mm Largo & 9mm Bergmann/Bayard.
The Spanish did this intentionally as their biggest exports went to Europe and the USA, both places where, at that time, .38 ACP and 9mm Bergmann/Bayard were abundent, 9mm Largo, not so much.
Again, and i can't say this enough,,,
The guns were NEVER designed to shoot the hotter .38 Super ammunition!
Don't use it in 9mm Largo chambered guns!
The Military guns, intended for issue to Spanish forces were only made to function with 9mm Largo ammo.
Of course, that elusive Bergmann/Bayard ammo will work fine in them also but I am guessing the powers in power didn't mention that fact to the rank and file soldiers who were issued the handguns,,,
Some will work with factory .38 acp, some require turning the case head down and turning an extractor groove on .38 acp/super cases and the cases will then work. You can load them from .38 Super dies but need to find a suitable shellholder.
Star, not being dummies in the gun manufacturing world, latched onto the modified breechface principle and I am willing to bet, most, if not all their 9mm Largo chambered guns used the dual purpose breechface.
If Star needed to make 9mm Largo guns for the military or .38 acp/.38 Super guns for the commercial market, the only change they had to undertake was marking the guns to the required/specified caliber.
Now 9mm Parabellum chambered Stars and Astras are different animals.
These guns were ONLY intended for use with 9mm Parabellum ammunition.
If you have one, DO NOT attempt to fire any of the longer 9mm/.38 cartridges in them.
Even if you get the cartridges to fit and feed from the magazine to the chamber, the end result will not be pleasant for gun or shooter.