Observation on Parabellum ammo

[unspellable]

I view the "Luger needs a hotter load." idea as an urban myth. The change to a shorter 9 mm cartridge contributes to the reliability problem. They are old and sometimes mismatched guns. The magazines have often been dropped once too often. Perhaps the majority of shooter grade Lugers have had their recoil springs tampered with and are out of spec. As Georg said, "The springs have to be right."

I share Sieger's experience, the Fiocchi 7.65 goes aross my chrono at around 1075 fps. The Winchester stuff is a bit spiffier but still not up to the original DWM specs.

As for load vs operation, the pressure curve has absolutely nothing to do with it. It's a RECOIL operated action, not a blow back. If you go to a slower powder while maintaining the same velocity you must use more powder. This will produce a greater impulse as you have to blow the powder gas out the muzzle as well as the bullet. The change will not be great, but if you were at the ragged edge to start with it, might make the difference. A change of 1 grain in the powder charge will be worth a change of about 1.5 grains in bullet weight in determining the impulse.