“I believe that for whatever reason, double stack mags in 9mm are more reliable than single stack.”
Interesting. Would you have any conjecture why this might be? I can’t think of any, but then I am certainly no expert here. Your experience could be correct, but it would be interesting to understand why this might be. If it is true for 9mm, could the same reasoning be true for other calibers?
I have done a lot of shooting with the 9mm. For whatever reason they have been extremely reliable no matter what the make or magazine size. I did have a Glock 17L which gave some problems. I later discovered the reason was a batch of magazines they produced.
I have fired thousands and thousands of rounds through other double stack 9mms and they all, including other Glocks have been 100% reliable.
I was once sort of surprised to get a malfunction with a Sig P225. I traded it off before I got another jam. Also had a few with an old P-38 and an S&W model 39. All those malfunctions seemed to be due to the front of the cartridge dipping down into the feed ramp.
Just playing around with loaded magazines and pressing on the front of the top cartridge, the single stack mags seem to allow the front to dip much easier than the double stacks. This may have something to do with the fact that the 9mm case has a lot of taper but that is just a guess.
Other auto pistol cartridges such as .40 S&W or .45 auto do not seem to have the same problem.
I don’t really know, that is just my guess.