Not trying to muddy the water, but here is a P320, fully in battery, notice the space between the barrel and slide. The Legion in you images looks to be about the same distance, although it appears exaggerated due to the extractor missing. If you look at the top the barrel hood, it is flush against the breech face. I believe this was a case failure.
I get the reloading for year and so on, but unless he is using once fired or new brass, there is always the possibility of a stressed case. It easy to make sure you don't overcharge a load, but very hard to see a hair line case stress fracture.
The 320's do appear to have a good deal more spacing between the barrel chamber and breech facing than some other pistols, and that along with any weakened or overcharged case could cause an issue. Lacking case support doesn't always mean it in the feed ramp area.
TXPO