This is long, but intended to educate. Read it all before going off the handle.
Most 9mm chambers are fully supported. There is a little area near the case web, by the head that is often part of the feed ramp that is unsupported, but this if normal, and an unsupported chamber is something altogether different. Read on.
Oh, and before you try and flame me, I own 4 glocks, 19, 20, 22, 30. Pretty much all the calibers, frames, and barrel legnths, so I know what I'm looking at.
Oh, JTDuncan, that thing about the 40 being a high pressure round is right, but stop right there! The 40 S&W is SAAMI pressure set at 35,000 PSI, the same as the 9mm. There is no SAAMI +P for 40 S&W, like there is for 9mm, 38, etc. If what you're saying is true, then us 9mm guys are also shooting a round that is prone to KB's!!!! Never mind that when you hit the primer, the powder is all gonna get really big, really fast!!! That's how guns work.
OK, here it is again, all the TRUTH about 40 Glocks, and why kb's happen to the 40 Glock. YES, it does happen to other brands and other calibers, but there is a MECHANICAL DESIGN REASON (which Glock will admit to if you talk to them) why Glocks are MORE PRONE to this happening to their products, especially with lead bullets. Oh, and their percentage of mishaps is higher than any other brand, which is not related to the fact that they simply sell more guns than anyone else. My dad is a gun nut, and a professional statistician (stock market) and he's tried and failed to support Glock with facts and figures related to the more production/more mishaps argument.
One is barrel rifling, and the other is the way that rechambering for the 40 S&W was achieved. Also, Glocks have a traceable and verifiable history of firing with the gun just slightly out of battery, which increases that tiny unsupported area just a wee bit! This info courtesy of 1911.com:
Some manufacturers of 9mm pistols simply rebarrelled, modified the breechface and put in a stiffer recoil spring to develop their initial .40 S&W pistols. Since the .40/10mm bullet is bigger than a 9mm, the only way to get the .40 to feed reliably was to create an intrusive feed ramp, and possibly an oversized chamber to match. Thus the .40 S&W "Unsupported Chamber" was born.
This was a quick and dirty fix by some manufacturers to get to market fast. Other manufacturers either started from scratch or went through the added expense to redesign their 9's to safely handle the .40 with a well-supported chamber that still feeds reliably. These types of .40 pistols are therefore safer to use, whether you shoot factory ammo or reloaded ammo.
If you want to find out if your .40 has a well supported chamber, then do this: Measure the diameter of the lower, most expanded part of some fired brass. After the first measurement, rotate the brass slightly and measure it again because the brass sometimes measures greater from a certain angle because of the 6-o'clock chamber opening affect. If your brass measures .431
or greater, then your chamber is entering into unsupported territory. Also, put a round into the barrel and look at the 6-o'clock position of the chamber opening. If the thin part of the brass wall is exposed, or too much brass is exposed, you have an unsupported chamber. "Both" of these measurements are important to determine if your chamber is well supported or not. The greatest brass expansion occurs when shooting full power loads.
The diameter of fully supported chanber brass usually measures around .427 -.429 for full power loads. The Glock .40 can expand brass as much as .431 .433, which is a huge difference.
Generally speaking, ammo and gun companies don't care about reloading safety and case life. Some of the newer reloading manuals have strong warnings about reloading for pistols with unsupported chambers, especially concerning high-
pressure cartridges.
One positive side effect of Glock's famous unsupported chamber and their marketing omnipresence, is that some ammo companies have beefed up their .40 S&W brass so it has a better chance of surviving when fired in a Glock chamber.
Tom
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A "Miss" is the ultimate overpenetration!
You can never be too rich, too skinny, or too well armed!
[This message has been edited by Banzai (edited April 12, 2000).]
