better question
Why is the PPK "double feeding" ? Not to be snarky, but what exactly is a "double feed"? If the PPK is exhibiting a tendency to fail consistently, I'd consider addressing the problem and not solving the resultant symptom.
First thing I'd do is detail strip and clean and lube....I mean an armorer's takedown. Then fire and evaluate. A new mag and ammo would be another step at this point. Many auto pistol issues are traced to ammo, lube or mag problems.
If the problem persists, determine what type of "jam" is occurring:
-fail to feed
-fail to extract
-fail to eject
Worn or weak mag spring, recoil spring, extractor or ejector can contribute to any of the 3 above.