If you use Speer plinker bullets and you taper crimp, setback is not an issue with the .30 Luger round. I made some cases from 9X21 CP brass and obtained some regular 7,65 Luger cases, and that holds true for all of them.
The Luger pistol is misunderstood by most American shooters. The sight picture is not the same as with a patridge sight. You have to bring the tip of the front blade all the way down into the bottom of the V notch (called "Taking a Fine Sight") to properly align front with rear blades. I've been doing trigger jobs on Lugers for over 50 years with no complaints so far.
If your gunsmith installs the proper recoil spring, you can shoot some heavy duty loads without too many problems. If you overload, you can blow out the extractor and will have to try to find a new breechblock.
The Luger does not begin to unlock until chamber pressure has dropped to absolute zero (Remove the extractor and note that the case remains in the chamber, but can be removed with a flick of your fingernail), so it will digest fairly stout 9X19 loads. On my personal Mauser made WW-II pistol, I have replaced the barrel and bifurcated barrel extension with a setup that is chambered for 9X21, and it feeds my favorite bullets without too much effort. The secret is getting a gunsmith who understands the Luger to work it over.
The most usual pistols that are used as shooters are the 1920 commercials, since they are the least expensive and collector desirable on the market. The newer pistols do not interchange parts with the older pistols. The older guns had hand fitted and numbered parts, especially the trigger system, and it is a little bit more complicated than just dropping in a replacement piece. Many "collectors" have substituted parts to get a number match, and more money from a buyer, and these guns are particularly hard to work with, some being downright dangerous to shoot.
If you want to avoid all kinds of heartburn, find a gunsmith who is competent to work on your Luger and don't try to "fix it" yourself.
The French destroyed the Mauser factory, especially the forging press in 1945, so none of the Mauser made parts are to original specifications. And, some parts for the Mauser made guns will not interchange with DWM guns without a lot of fitting. Barrels are finicky. I've seen some that have 60 degree threads that expand the receiver ring when screwed home, jamming the pistol big time. They should be 55 degree threads and preferably have a short chambered barrel so that the gunsmith can regulate headspace.
