Are you sure you popped a few caps before loading to clear the nipple and fire channel? I have never had Pyrodex give me any delay in ignition. Whether Pyrodex P would help, I guess you can only try. I also use Pyrodex P in a couple of rifles but like I said, I never had any igniton problems with it. Are you using the original Lyman nipple? I have heard people had problems with them.... just a thought.