Eric, welcome to the forum!
If it is a 1915 DWM, then the barrel was put onto it, or it was relined. I have a 1912 DWM that was relined to 7.65mm (also called 30 luger). You can measure the bore if you have a micrometer.
I will move this either to new collectors or to the military section, as early lugers are usually considered before ww1.
Can you provide pictures?
Does it have "germany" stamped anywhere on it?
Ed