I'm glad to hear you get good performance from your Glock. Had my experience been positive I might have been a fan as well. It is interesting though that you state a preference for a SIG despite all the Glock shooting you have done, perhaps you've been mandated to carry one and had to develop a measure of comfort with it. SIGs have issues as well, aside from the sticker price, but had I to choose between a Glock and a SIG, the decision would be easy. You are correct that my horizontal groups are a result of not spending enough time with the Glock, but seeing that I'm comfortably into middle age now, I doubt I will live long enough to get a horizontal group with all the holes touching to morf into a round group from a gun with a 20 pound trigger. Although I did say that had that been my gun, I'd have fixed that trigger, probably by throwing the gun into Hudson Bay, and going back to one of my 1911s, or even a revolver.
Getting 2 hits in one second, including reaction time and draw is very fast, as fast as most people's reaction time alone, you are to be commended. Of course you are ready for the signal that you know is coming which is the downfall of any timed drill, whereas on the street what matters is how quickly you can deliver a shot without being forewarned of the need.
I would like to know what you thought you accomplished by weighing your ammo though. A bad primer weighs the same as a good one, and if you have a heavy casing and a heavy bullet that is more than enough to mask a light powder charge in a service pistol cartridge. If it makes you feel better though, carry on. A bad round can occur from any manufacturer, from any batch number, regardless of how much testing is done. The testing that is involved in the quality control of ammunition only tests the round that is being tested, not the next one, or the one that is in your chamber. If you ever experience one, it might be that one in a billion failure, but if that is the round in your chamber when you need it, it doesn't help you. I wonder if you would pull the trigger a second time or rack the slide? I'll bet you'd pull the trigger again, and probably get the same results. With a 1911 you'd be more inclined to rack the slide. I've pointed this out to others who must put absolute faith in their ammo when they engage in their high risk professions, and like them you probably won't consider the possibility relevant to your experience, besides, you're not going to live forever, right?
That fact that you drill to clear a stoppage is far more important than weighing pistol rounds, I hope your drills are not limited to a single type of stoppage. In a real fight, you might not get that magazine securely locked in after a speed reload. The fastest and surest means of dealing with a stoppage is by carrying a backup as you can draw and fire with your weak hand faster than you can diagnose, clear, and reload a stoppage in your primary.
I dislike the simulated gunfight exercises with non-lethal rounds. Aside from the possibility of a lethal round finding its way into a magazine, and that has happened, it messes with your mindset that that thing on your hip is a lethal weapon. I never want to loose that discomfort that must be overcome even in a fight when my front sight covers a live human being. But if that's the way you train its none of my business, at least you get the idea that a human target can shrink in front of your eyes by simply quartering towards you.