Pennsylvania Museum has a .303 Lee Enfield similarly chopped down.
It came in with weapons from the 28th Division after World War II.
The tag on it said that it had been used by an Allied POW to escape from German captivity.
True or not, I don't know.
Where would you have found much .303 British ammo in Germany, though?
If I had to do that, I'd have used it once to take down an isolated soldier somewhere, and take something like a Schmeisser that could be easily concealed in a coat? (and then try to look as German and inconspicuous as possible while trying to get on a train out of Germany!)
Unless they mean it was just used to get out of someplace, which I could see. I'd be curious as to the full story of it!