You didn't say what kind of powder. If it's Bullseye, Unique, W231, or some light flake powder like that, slight compression will cause no problems. Most reloading manuals include a notation or asterisk where the recommended charge is compressed, so you won't worry when you discover that this must be done.
I prefer not to do it, but have done so when required. I would not do it with a relatively hard, long grain powder, as rifle powder. And in most cases, where compression would be "required" to fit it into the case, the charge would be dangerously high.
Check to see that the last fraction of an inch of the lands in the rifling of your PPK barrel have been properly reamed away, relieved, at the factory. Even Walther makes mistakes. If the lands go back all the way to the front ledge of the chamber, they would cause the problem you describe, and should be relieved.
My progressive reloading press once caused a powder compression problem I only discovered on the shooting range. Some 9mm rounds were getting a DOUBLE CHARGE of Bullseye, compressing it by about 100%! Happily, I was shooting a heavily overengineered Uzi. Nothing broke, but the bases of the brass cases were being partially extruded into the ejector slot in the bolt face. Don't try that at home.
