I have researched the P6 feed ramp issue and found the following post on SIGforum ...
"Dear Mr. xxxxxxx,

We checked our drawings and found out that we change the angle of the barrel ramp on the 14th of June 1989 from 52 degrees to 54 degrees.

Mit freundlichen Grüßen,
With best regards,

Ralf Vanicek
Produktmanager SIG SAUER

J.P. Sauer & Sohn GmbH
gegr. 1751
Sauerstrasse 2-6
D 24340 Eckernförde"