Velkommen Jan Erik,
as a former officer in the norwegian army (not airforce
), I still recall the days where a Luger on the belt was a common sight. Usually guard personell, medic or low priority homeguard divisions had them. There was better alternaties back then (Colt, Browning HP..), so most people having the choice, did not go for the Luger.
Back then, it was not the NATO ammunition I'm guessing you was shooting that was used (those white boxes containing 50 rounds). It was the gray 16 rounds boxes made by Raufoss. Both are too hot for the luger and especially the post war P38's (in which I would not dare to fire a pea in!). The first NATO ammunition had warnings about this on the label, but the warning disappeared as the last Lugers faded away in the late 90s(!).
The thickness of barrels, usually cut down Shmeizer barrels or Lathi replacements, had nothing to do with making them more functionable. But was mostly a result of the winning instinct amoung the officers competing in shooting events. I have never seen a modified Luger in regular military service.. Hard ammunition is neither the cause for the jamming. Loose grip, bad maintenance, cold weather, bad luck..