Hi Steve,
Well, I can tell you that one of the more famous Panzerjäger 'aces' of the war, Ritterkreuzträger Hauptmann Albert Ernst, served in the same unit as your Grandfather, although Ernst commanded the 1. Kompanie. JJ Fedorowicz Publishing published a book by Franz Kurowski called "Panzer Aces" in which his story is told. You can read a tiny bit of it here:
http://www.achtungpanzer.com/pz2.htm.
Here's the reference data I have on the unit:
schwere Panzerjäger-Abteilung 519 (Hornisse)
1. Creation
25.8.1943 in Spremberg, Wehrkreis III, with 3 companies (plus a staff company); reorganized on 15.9.1944 as schwere-Panzerjäger-Abteilung 519 (Panther) in Mielau, Wehrkreis I, and re-equipped with the Jagdpanther.
2. Employment:
Heerestruppe: Russia; transferred to Heeresgruppe B (Western Front) 10. 1944.
3. Replacements
43 Spremberg, Wehrkreis III
This image is supposed to be a Hornisse/Nashorn of sPzJägAbt 519:
http://klub.chip.pl/krzemek/nashorn/nashorn_13d.jpg
You can even build a model of a Nashorn from your Grandfather's unit:
http://pmms.webace.com.au/reviews/vehicles/dragon/dr6166.htm I actually did
They apparently fought with the 6. Luftwaffe Feld-Division in late 1943, early 1944
http://www.battlefront.co.nz/Article.asp?ArticleID=510, and they were attached to the 9. SS-Panzer-Division (II. SS-Panzer-Korps) for Unternehmen 'Wacht am Rhein' (the proper name for what the western Allies called the Ardennes Offensive)-
http://www.axishistory.com/index.php?id=629. I read elsewhere that this is where the unit employed 7 Jagdpanthers, although I don't know how these were distributed among the Kompanien.
I hope this helps.
Matt
Let him who is without sin cast the first stone.
Pluralitas non est ponenda sine neccesitate- "Entities should not be multiplied unnecessarily'' William of Ockham