i found the same thing (shooting way low) on my Sig P225. when i mentioned to an instructor at my gun club, he asked if he could give it a try.
i cover the with the site, but he used the 6 o'clock position and hit dead center. he said he thought i might be pushing my hand forward right before the shot in anticipation of the recoil, which pushed the barrel down.
i fired another box through it and was able to correct the problem. might give it a try. my 82 shoots exactly where you point it!
i'm looking for a deal on the meprolight ml-17777 for the 82, which i hope will make it a little easier to align with target.
rick