You didn't mention if you were loading a mag with the bolt open or closed...
If "open", try loading the mag with the bolt closed, to see if round #1 in that condition does what you say or groups with the other rounds. That way, all 10 rounds will enter the chamber under the same conditions, with pressure from the mag spring from below, and hitting the bolt at the top. It's possible the lips of those 2 mags are just different enough that they allow the round to bounce up or whatever and it enters the chamber differently than all other rounds that follow with a closed bolt.
Here's another thought, try those 2 mags only, with full rounds loaded. Load the 1st round like you always would -- but eject the unfired round instead. Then load and eject rounds 2 and 3. Using a magnifying glass, see if you spot any differences on the nose of the bullets between those rounds.
You can also using the magnifying glass to closely examine the feed lips of the trouble mags versus the others that work OK all the time.
"Something" is different, and a few controlled tests like this might help you find out what it is.
Tight groups.
Old No7
Bookmarks