Just one guy's opinion:
Glock worships at the alter of reliability (not a bad idea considering the mission) The chamber support or lack therof is all about feed reliability under any and all circumstances.
The 9mm is a tapered cartridge, which really helps with both feeding and extraction, and therefore really doesn't need any help from a generous feed ramp and throat. In short, it's an inherently reliable cartridge.
The "other" cartridges are relatively straight walled, so IMO Glock gave up a touch of safety margin (relying on the ammunition manufacturer to get it right) in order to produce the most reliable pistol in the world (you be the judge of whether they succeeded - I dare anyone to call them un-reliable though)...(okay, I know one smart ass will call them unreliable...I asked for it)
So why doesn't everyone just design their cartridges with more taper like the 9mm? There's a few reasons:
1 - Tapered cartridges tend to be less accurate than straight walled cartridges
2 - A tapered cartridge wants to push out of the chamber when fired. This means significantly more back pressure on the bolt face. Look at the M1 Carbine (very strong taper) and the M1 Garand (tapered, but not too bad); cracked bolt locking lugs were not uncommon at all. This is from the greatly increased back pressure of the tapered cartridges. So in short, tapered cartridges = shorter life span of the weapon. (but admittedly not much of an issue with the 9mm until you really get to NATO pressure)
I agree with all of your post except one thing. Glock (and their users) *do* worship ultimate reliability. 9mm Glocks are some of the most reliable and best fighting guns out there. However their .40's and .45's are suspect. I'd challenge anyone to find a 9mm Glock that KB'd, and if it did I agree with the Glock camp...probably the ammo. Heck, I even just suggested to a friend that he should look at a G19 or G17 for his first handgun.
Their .40's and .45's however don't have unsupported chambers due to them wanting to *increase reliability*. Their unsupported chamber is almost a requirement of the design dicated by the mag to barrel placement. To get these big rounds into the chamber with a round feeding so close to the barrel like Glock's one of two things have to happen:
1. You move the barrel forward, increasing the space between the barrel and mag and allowing the round to properly feed.
Problem here is you ruin Glock's second dictum: compact weapons. This would make their .40's have to be redesigned from scratch instead of just altering their 9mm design. And their .45 design was from scratch, but to keep the weapon as compact as possible (and to keep erganomics the same across all their weapons) the mag to bore relationship stayed the same.
2. You allow the ramp to protrude into the chamber resulting in an unsupported chamber.
We all know the problem with this so no use in beating a dead horse. However as shown by the pic of the 1911 barrel, Browning never designed the round to be unsupported. Way back in 1905 with the inception of the .41 caliber that the 1911 was designed originally for, up through 1910 to when it was redesigned for .45 at the US Army Cav's requst, it was designed as a fully supported round.
Other manufacturer's took this to heart and incorperated it into their weapon designs. Look at the H&K USP barrel, or the HK45c barrel posted on page 1...both are fully supported, the 1911 barrel is fully supported too. This does lend other compromises in their design however that people *do* bash on. The 1911 has feeding problems because it doesn't have a large ramp, and without some tuning, reliability suffers. H&K moved their bore axis up for a couple of reasons (FCG is probably the main one), but the high bore axis allows them to use a massive ramp. I'd doubt anyone calls a H&K USP .45 or H&K SOCOM unreliable....but you do hear complaints about the high bore axis and resultant increased muzzle flip.
Basicly it boils down to this, all mechanical designs are a compromize. You are always giving up one thing in return for something else. Glock had/has one of the best 9mm pistol designs on earth. And they decided to capitolize on that by offering their pistol in other calibers to increase sales/market share. To keep the pistol basicly the same their were compromizes they had to make, and if it were me... I'd choose to have a little more muzzle flip...or perhaps a FTF once in a while...compared to a KaBoom. Because the FTF can be quickly resolved and you're back in the fight. Your gun goes KB, your hand may not be blown off but you are left without a gun in a gun fight...not a good place to be.
I've always really liked this one to!