So . . .
Mag with 10 rounds inserted into a Glock. Spring and follower are exerting enough upward pressure to allow slide to strip and load top round into chamber.
The gun fires. The slide retracts. The first case ejects. The second round rises, is at least partially stripped from the mag, but jams. Working the slide clears that cartridge but the next cartridge cannot be stripped from the mag. Mag is discarded. New mag loaded and back to normal firing.
On inspection of dropped mag, top round is in the mag backwards, but under pressure from follower, not rattling around above a stuck follower with cartridges falling out of the mag.
So, at what point did the third cartridge turn 180 degrees if not initially loaded backwards?
Not when the first round was stripped under sufficient follower pressure. The stack under pressure would not allow the third round to turn.
Not when the second round with enough upward follower pressure to be stripped out of the mag moved forward although it did jam. No room in the mag for any cartridge to turn.
So if the stuck follower is the explanation for this stoppage, it appears the follower must have stuck while the second round stripped from the mag under follower pressure was causing the stoppage. IOW, with about the width of one cartridge above a properly loaded third round (now in second position) but no pressure from underneath because of a stuck follower, the third round jumped up its full cartridge length (roughly three times the width of a cartridge) under the feed lips, turned around vertically 180 degrees and fell back down into the mag. At some point, whether through racking the slide or dropping the mag, the follower was probably jostled loose, and upon subsequent inspection the top round in the mag, under follower pressure, was noted to have turned around backwards.
I admit a cartridge can turn 180 degrees vertically in a mag with a stuck follower and no spring pressure from below, BUT ONLY WHEN there is enough room above it to do so. In order to be stripped by the slide from a mag, a cartridge must be at the top of the mag under pressure and properly oriented forward. When the follower sticks after two (or any number of) rounds have been fired, there is only ONE cartridge width above the top unpressurized round with the mag in the gun. IOW, the slide strips rounds from the mag until there is no round riding at the top to be stripped. That is only a one-round deficit at the top of the mag--not two or three.
Out of the gun, with only one cartridge in the mag and the spring removed, I held the follower in place from the bottom. Leaving enough space above one cartridge resting on the follower to represent one missing (stripped) round above it, it was not possible to get a 180 degree rotation because the feed lips prevent it. This is two cartridge widths. I lowered the follower until I could rattle the one cartridge around to being backwards. This was three cartridge widths. It took A LOT of rattling, and of course there were no other loose rounds below this one cartridge also moving and taking up vertical space.
This is a manufactured, controlled experiment that absolutely proves a round can turn around in a mag under conditions not possible to duplicate with the mag in a gun that has just stripped the top two rounds out the same mag. You have to have at least two cartridge widths above a third round before it can turn in a mag. If even one round fires from such a mag under proper follower pressure, then there can only be one cartridge space missing.
So . . . is it possible that the third round was loaded backwards and still under proper follower pressure? The first round stripped and fired. The rim of the second round, under follower pressure while being stripped, hung up on the forward oriented rim of the next (reversed) round below it, also under follower pressure, causing that second round to not chamber. The extractor was hooked on the rim of the second cartridge, so retracting the slide ejected that unchambered round. However, neither the extractor nor the face of the slide could strip the backwards loaded round (bullet facing rearward) from the mag, causing another stoppage. This was cleared by dropping the mag.
Sometimes the simplest, most easily explained and reproduced explanation is the correct one. Hard to admit. Human error. If this logical, observable, reproducible, mechanically possible and probable stoppage explanation makes me a "clown", I am willing to live with that moniker.
Can cartridges turn in magazines under non-field conditions? Yep, if set up unrealistically there is space. Under field conditions with previous round(s) having been stripped from the mag under follower pressure? You decide.
