I've got two p15s. Both now in 177 and they're stupidly accurate. I've polished the bore/crown and breech areas on both with autosol. Open TP a fraction and eased hammer preload slightly. Both 11.3ftlb with qys pellets which are fractionally better than jsb and jsb neavy
One came as a. 22 cal but that barrel isn't the best to be honest. Gave that one a Blean and polish but it never came good enough to hint, in my opinion. Perhaps I'll revisit that barrel for another go.
I love mine and the carm mags are a superb upgrade.