9mm Largo vs. Others
This is a standard reply. I have to address this fairly often, so to save time I saved this reply as a txt document.

The vintage 9mm Largo firearms that are available were not designed to be fired with .38 Super ammunition!

The velocity and muzzle energy of the original 9mm Largo ammunition is higher than most of us load to for our Largos, a little lower than .38 Super, lower than 9x23mm Winchester, and about on par with .38 ACP. Some 9mm Largo pistols will chamber the semi-rimmed .38 ACP and Super, some will not. The only Spanish data we have on the original 9mm Largo load specifications is not in American style data. The pressure is specified as “less than XXXX kp/cm2.” We do not know what is meant by “less than XXXX kp/cm2.” Is this the pressure of an overpressure test cartridge (used only in testing of new firearms), or is this the service pressure limit?

You need to realize that all weapons have an expected service life. This is normally measured in 'number of rounds.' This is the point at which the firearm is just plain wearing out from pressure forces and mechanical action (i.e. the slide moving in the rails). When your firearm was brand new the metal was strongest and perfectly in specification. As it approaches the end of it's service life, it gets looser and weaker. Where is your firearm in its service life? How many rounds did the previous owners shoot out of it? What was the expected service life of these pistols 20,000 rounds? 10,000 rounds? No one knows.

The metallurgy of your pistol was not designed to handle .38 Super pressures. It was designed to handle 9mm Largo, and some of them were designed to chamber .38 ACP. When the pistol was new it could probably handle a certain number of .38 Super rounds. As it nears the end of its service life it gets weaker from containing the pressures of firing and the mechanical action of functioning. Firing .38 Super in your 9mm Largo firearm is much like firing +P+ ammunition in a firearm not designed for it.

Some people will tell you that all you have to do is change springs. They are not the only item in the equation.

A major reloading company worked up loads for 9mm Largo using a Star Model A and virgin Starline brass. These loads approach .38 Super levels. They were not, however, able to do destructive testing with factory new firearms, nor were they able/did they to the best of our knowledge take measurements of frame stretch or changes in the structure of the steel in various parts of the firearm to check for crystallization of the steel. There are no SAAMI/ANSI specifications for 9mm Largo that I am aware of.

Please, stick to 9mm Largo ammunition in your 9mm Largo firearms. If you just gotta have a .38 Super, buy a .38 Super. There is plenty of Surplus 9mm Largo ammunition available out there, CCI loads 9mm Largo in its Blazer line, and virgin brass is available from Starline for reloading. If you need a source for surplus 9mm Largo, let me know.

In the end, it is your call. I do not fire .38 Super ammunition in my 9mm Largo firearms, nor do I load my 9mm Largo reloads to .38 Super levels. I know people that do and have for a long time without any problems. Is that little bit of extra boom when you shoot it really worth taking the chance of the pistol failing in some way shape or form? Is it worth your eyesight?

The only specific information that I have on the Astra 400 in reference to using .38 Super ammunition in it is that the firearm was never proofed with .38 Super ammunition. This ammunition didn't even exist when these pistols were developed.

I will give you this comparative information from Cartridges of the World by Frank Barnes.

9mm Largo
Bullet Diameter:.355
Neck Diameter: .379
Base Diameter: .390
Rim Diameter: .392
Case Length: 0.91
Cartridge Length: 1.32

9mm Bayard Long (pg. 234, 7th ed.)
"The cartridge is quite similar to the 38 ACP, but longer. The Astra Model 400 is designed for the 9mm Bayard and will handle the 38 ACP without any adjustment..."
(ED: 9mm Bayard Long is another name for 9mm Largo. The comment about Astra 400s is not entirely true however. Only some of the Astra 400s have the 'compromise' breech face that will accept the semi-rimmed .38 ACP)
Bullet Diameter:.355
Neck Diameter: .375
Base Diameter: .390
Rim Diameter: .392
Case Length: 0.91
Cartridge Length: 1.32

38 Colt Automatic (pg. 238, 7th ed.)
"In power, it is about the same as the 9mm Luger, but it has a longer semi-rimmed case."
SAAMI Pressure Max: 26,500 CUP
Bullet Diameter:.358
Neck Diameter: .382
Base Diameter: .383
Rim Diameter: .405
Case Length: 0.90
Cartridge Length: 1.28

9mm Steyr (pg. 231, 7th ed.)
"The 9mm Steyr is a pretty good field cartridge, similar to the 38 Colt ACP in performance."
Bullet Diameter:.355
Neck Diameter: .380
Base Diameter: .380
Rim Diameter: .381
Case Length: 0.90
Cartridge Length: 1.30

38 Colt Super Automatic (pg. 239, 7th ed.)
"Introduced by Colt in 1929 as an improved version of the older 38 Auto. The Super Auto is identical to the original cartridge except it uses a more powerful loading and has a higher velocity."
SAAMI Pressure Max: 33,000 CUP
Bullet Diameter:.358
Neck Diameter: .382
Base Diameter: .383
Rim Diameter: .405
Case Length: 0.90
Cartridge Length: 1.28

So, based on Barnes' information, would you fire .38 Super in a 9mm Luger firearm just because it would chamber.

Indicators of incipient failure of a firearm due to excessive pressure: cracks in pistol frame, bending of frame, cracks in slide, bending of slide, cracks in chamber area of barrel, bulge in chamber area of barrel, pistol slide protruding from your forehead, pulling the trigger and being left with only the grips and lower portion of the frame in your hand, pulling the trigger and not being able to see the target afterwards or anything else for that matter. Granted these last three are indicators of failure, not incipient failure.

Once again it's up to you. I however do not encourage it. You will hear reports from shooters all the time that they have always fired .38 Super in their Largo firearms and have seen no ill effects. Hey, it's your firearm, it's your eyesight; I'm not going to do it. I've also had people tell me that as long as damascus barrels don't look rusted that they are safe to shoot, even with modern smokeless ammunition. If I just had to fire an old damascus barreled shotgun with any ammunition, I'd have it electronically examined for microscopic corrosion between the layers and strands of steel in the barrels. Heck, I even knew a guy who turned his .22LR rifle into a .22WMR with a drill substituting for a chamber reamer; hey, let me stand over here while yo fire that.

I probably sound like a broken record, but don't let it be said you were not warned if something does happen.

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