I got three war time P.38 (cyq/cyq/bfy) and one P1 (1957, Berlin Police, refurbished). The un-matched numbers byf (Mauser) is the most accurate and the one one that cost me the less. All four love the same recipe: 4.4 gr of 700x, COAL=1.100", 115gr FMJ. Clock at 1140 fps (a little below ordnance value, but easier on the oldies and better grouping). Be aware that the aluminum frame of the P1 are known to crack in the long run, so refrain from P+ ammo on these ones.
What a very , very fine sidearm! First 9mm DA, 1935 design. Love the "chamber loaded" indicator. A natural pointer. Not as ###y, nor as accurate as a P/08 .30 Luger, but more reliable and tough.
On surplus ones (vs arsenal refurbished), check that your de-cocking lever is operating correctly. If not, the part to change is cheap (8$). Buy it from Tradex! however, as the ones provided by your seller are not machined correctly.
With the SIG P226, this is the simplest pistol to tear down and re-assemble that I've come across. In fact there is one part less (the springs stay with the frame on the P.38). Learn it till you can do it in obscurity. Gefreiter.