I Googled "Fangschuss-Geschoss" and came up with what you were referring to. It looks like a 125 grain deep hollow point gilding metal jacketed bullet. I have never used anything like that on deer, but I did shoot a couple last year with my .308 using 130 grain SP bullets I normally use for target shooting at 200 yards, and they killed quite satisfactorily, even though I am satisfied that they would be classified as varmint bullets by their manufacturer.

The second buck was shot through the shoulders, breaking both of them and trashing the lungs, but he made it about 100 yards on his hind legs alone, a truly amazing performance. The first one moved just as I shot and was hit a little far back, but made it only about 150 yards. I wouldn't hesitate to use that load again. No exit wound on either one, and very little blood, which would be one drawback.