PPKs have a long and checkered past mainly because they have been in production for so long and have been made by four different manufacturers (Walther, Manurhin, Interarms and S&W) in three different countries and under several different sets of political conditions. Even the Walther factory has relocated at least once (originally in Thuringia, then when that became part of the Soviet Zone of occupation later the DDR; Walther engineers fled and the plant was relocated to Ulm/Donau in West Germany.) Post-war PP's and PPK's were made with the Walther banner but under license in France ! . As you know, Walther pocket pistols are currently made by S&W under license. The other American made Walther was made by Interarms which was primarily a CIA connected arms import/export firm. (The history of Interarms in and of itself is a topic worthy of a book). Quality control has varied as well, a PP or a PPK made under late WWII conditions will not nearly be as well made or finished as its pre-war or post-war counterpart, for instance. There appears to be a consensus among Walther fans that the Interarms made guns (produced in a factory in one of the US Southern States) as opposed to the Interarms imported guns were not as well made as their European counterparts. Both the PP and the PPK were designed to fire hardball ammunition in their original designs.
There are simply too many variables therefore to make a general statement about the PPK, other than it should perform reliably with hardball. Certainly, newer specimens of the pistol will probably fire hollowpoint rounds reliably, but I still think that even that can vary from individual gun to individual gun. S&W (as much as I have an emotional and small financial attachment to the firm) has developed a reputation for inconsistant quality control, so one batch of pistols might be just fine with hollowpoints while another batch might have real issues with it.
The only way to tell, is to see how your pistol works with various types of ammunition.
Mark L.