There's a 1944 US Army document declassified in 1958 that appears to give penetration for this weapon. Go to page 22 (page 166 of the original document):
http://www.scribd.com/doc/13810712/S...log-1944-Vol-2
It's difficult to read, and you'll have to zoom in, but if I'm reading it correctly (not sure that I am) it gives this penetration (homogeneous plate) at 20 degrees:
............AP......APC
500yds....81......71mm
1000yds...69......64mm
2000yds...53......53mm
Hope this helps,
Cross