I think you meant that the other way around.... Can’t fire 9mm Para through a 380, but can fire 380acp in a 9mm chamber.
I don’t think I said one could fire a 9mm in a .380... I made a statement that a
defense attorney may use the various headstamps to claim multiple calibers (“9mm,”, 380) were present. This is to confuse a jury who may not be gun-savvy, and who won’t catch that these are not “9mm”(Luger) rounds, but are all just different names for the same thing.
I had one case several years ago where the three defense attorneys representing three gangster defendants (tried together) have done this exact thing. One kept referring to the 9mm Corto (Sellier & Bellot if I recall correctly) headstamps found along with .380 Auto (aluminum Blazer) headstamps at a shooting as different calibers.
There was only one .380 present that their gangster client was shooting, the other gun fired at the V by the second defendant was a .32.
The defense attorney did this on purpose, trying to claim there had to be three guns there, “a 9mm. ,a .380 and a .32”..so it was a self defense situation because the V had a 9mm handgun that the cops “purposely didn’t find” because they had it in for their clients. It was a good defense ploy, I give them credit.
I spent a good 45 minutes on recross explaining to the jury the multiple names this caliber goes by (thank goodness for a whiteboard!) and the forensic examiner spent a couple hours showing the microscopic marks were all made from firing the same .380 ACP gun.
My instruction is for these DDAs to be prepared for these tricks and to be sure they elicit the proper testimony to clarify this from their LEO witnesses (who also aren’t always gun-savvy!) or from me if I’m called as an expert witness.
And yes, I have fired a .380 in a 9mm Sig P-226... it did fire but didn’t have the oomph to cycle it.
Most crooks aren’t very gun savvy either. I’ve also been on a scene where some crook had a mixed-ammo magazine and a .45 GAP round fired but jammed a .45 Glock. Another time some guy had two .40 S&W ammo rounds mixed in at the bottom of a 1911 mag with five .45 ACP rounds on top. I have no idea how the .40 rounds stayed in the mag when it was loaded, but it was in there. These cases are always fun to explain.
Stay safe.,