[John Sabato]

Most likely the magazine is the issue. Do you have more than one? Or do you know someone else who shoots a Luger that you can try their magazine(s)?

The likely cause is that the notch in the magazine that retains it in the pistol may be worn to be too large and the magazine sits low in the gun. You can test this theory by resting the gun butt in the palm of your non shooting hand when you fire. This will push the magazine higher in the pistol.

If you successfully load the second round when using this technique, then you will have confirmed that the magazine (or that part of the magazine catch that holds the magazine) is at fault. Use Winchester FMJ ammo for your testing. It generally works well in all 9mm Lugers. You can normally find it at Walmart, but many have been sold out for months...

Welcome to the Luger forum. Please post photos of your Luger with a longer barrel, and let us know the results of your testing.