i see you already have your answer but i will write my opinion. even if the guns original manual states that you can safely dryfire(which i have never seen any manual say yes,go ahead dryfire it as much as you like) unless there is some specific reason of it's design that you can do so,i still wouldn't.
allways use snapcaps.the reason why is that without a round or a snapcap in the chamber the firing pin or striker doesn't have the primer to hit which also limits its travel.the snapcap atleast acts sort of like a buffer. so if there is nothing in the chamber and you hear "click",what is the firing pin hitting? it still hits but not what and where it should. this causes undo stress on the striker,especially in the long run.
if you have a pistol with a hammer,you can also place a thick rubber o-ring right where the hammer strikes. i actually prefer this method with hammer fired pistols. i try to place the o-ring with the firing pin right in the center so it doesn't even make contact with the rubber. its really great to smooth up the trigger a little and even after a hundred pulls the firing pin hasn't moved or been touched.
i am absolutely not going to mess around with the trigger on the p99.i think it is perfect just the way it is but for practice snapcaps do the trick.
