Loose rails and accuracy

[4 Scale]

I have a Luger that had play between the frame and barrel extension/receiver. Like yours, it rattled and depressing the trigger moved the upper to the right. So much so that the grip safety did not work. A weld to add metal to the upper coupled with careful filing/fitting by my gunsmith fixed the issue. However, before and after the fix the pistol was very accurate. As Don explained, even with play between upper and lower the Luger should be accurate.

You might test to see if the safety works.

I suspect the barrel is the issue and would inspect that first. If no issues are detected consider adding metal to remedy the play issue; I suppose at some point too much play might impact accuracy.