Please excuse the long description.
The original barrel's feed ramp apparently was modified, producing Bulged brass. A club member who knows German WW2 handguns told me that "the brass is not supported". But it feeds very well, though I stopped using that barrel.
When the replacement barrel and slide arrived, I saw that the feed ramp looks and feels smooth. The tiny area of the frame's surface between the inserted mag and feed ramp also feels smooth.
I'm a novice with handguns and my only prev. handguns are the superb Sauer 38H and Sig 232.
Much of the time when the Hsc's magazine is inserted with the New barrel, the round only strips part way in the feed lips, with the slide jammed.
Even when mag. insertion is fine and the first shot is normal, numerous succeeding rounds only go part way fwd. in the lips.
The ammo is recent fmj: Sellier & Bellot 7,65.
Even with this newer barrel in my original slide, rounds are not stripped more than part way forward.
Extra slide/barrel, matching #s 503: "Mauser A.G. Oberndorf a. Neckar". I've recently spent $500 buying this gun and $240 for the extra slide/barrel, though the firing pin is a rare, valuable spare.
