Just for reference if not deleted (I assume you saw the short-barrel thread which refers to the LC9)...
I carry Speer Gold Dot 124gn +P without any failures (have fired about 20).
Here is a link to some different ammo tested in the gun:
http://www.goldenloki.com/ammo/gel/9mm/gel9.htm
They were tested in the P-11 which is the double stack version, but same barrel.