Originally Posted by
Arclight
Sure, I'll weigh in here. Short version -- I was always trained to use the overhand method based on "gross motor skills" and "most reliable" and such, especially as a lefty. While I have mixed feelings about the former argument, I have proven that the overhand can be more reliable as far as gun function goes. (More on that later.) As I started to speed up, however, I had a couple of instructors encourage me to try using the slide release instead, since it's significantly faster. At first I found it impossibly fiddly and rejected the idea, but eventually Todd talked me into giving it an honest try and, with some practice, found I could shave real time off my reloads and do it as consistently as the overhand rack (which itself can be tricky if your hands or gun are wet).
As far as how to use the slide release (slide stop lever?) as a lefty, here's my preferred method: When the heel of the support hand seats the magazine, the first and/or middle finger of that hand reach around and pull the slide release down, releasing the slide. (To visualize, simulate where your hands would be as the magazine is seated. Unless you do something funky with your hands, the support hand is probably spread with the fingers on the side of the gun where the slide release is.) While this isn't quite as easy as it would be if you were right handed and could just use your thumb, it does work well with practice. It also puts your support hand much closer to where it needs to end up than it would be with an overhand slide release, so I find it to be much faster. You *may* want to change the size/shape of your slide stop lever if you find it hard to catch in a hurry.
So, back to reliability. I normally shoot a Gen3 G19, and this method works perfectly with that gun. However, I (used to) occasionally shoot a G34. What I found is that the slide release method was not always giving me enough forward force on the slide to fully seat it and I was getting malfunctions (not frequently, but my G19 has never malfunctioned in ~8k+ rounds, so this got my attention). I talked to a bunch of Glock armorers, including one resident here, and a few of them pointed out that Glock doesn't consider that lever a slide release, but rather a slide stop. The "official" method for sending the slide forward is the overhand rack. Apparently some of the bigger guns (or possibly as the springs age, get dirty, or a combination thereof), need that little bit of extra tension and clean release gained in the overhand movement to seat it fully every time. I'm not 100% sure that's the diagnosis, but I never had that problem when using the overhand, I exclusively had it when using the slide stop, and all the mechanics seemed to work out when I tested it dry. Sometimes it just didn't go quite all the way into place. For the record, I have since adopted two G17s (g3 and g4) and neither has any issue with the slide stop method.
The best advice I have for lefties is to put a bunch of range and dry fire time into whatever method you think will work best for you. Then go take a class or compete (or something where you've got a bit of stress on you) and see if the wheels come off. 99% of the time, I find the underhand slide release method is perfectly doable under stress. That said, I still find that when I get really stressed, my lizard brain goes back to the overhand rack, and I'm okay with that. Just shows that the years of training I put into that early on have stuck with me.