Not to hi-jack the thread; A reply to "bastardsonofelvis", if the piston chamber has been worn to be out of spec ...the p7 is NOT toast. Two of my p7's have well over 100k rounds thru them. The M13 had in excess of 125k and 3 replaced pistons. It required a new piston chamber as it was .010" too big. I bored out the old chamber and fabricated a new one, which I then pressed in place.
It was a big job at the time because I was flying blind with no experience. After having done one, I can say that the hardest part of the job was fabricating a jig to press out the barrel and press in the new chamber.
That "well used" M13 now lives near Miami in the hands of a LEO who uses it to shoot IDPA/USPSA regularly.