Unsupported Chamber, is it really?

[hobowh]

great info thanks

[Colorado Osprey]

I've only ever witnessed 2 KB's.

Neither were Glocks... but both were 40S&W

I think it is an issure primarily with the cartridge's higher pressure. If the Glock chamber was truely the issue, why don't the 10mm's explode?

The 2 guns that chunked were a Ruger P91 and a Beretta (Italian) 96.

Both guns were sent to the manufacturer and replaced by the factory.

The ammo was commercial re-man training ammo by different comapnies about 5 years apart.

[Hannu]

As an engineer, I just need to say something techical

Supported / unsupported chamber is an interesting question. I would say, we can not compare different calibers because they have pretty different case design. For example, 9mmx19 has lot's of taper but .40 does not.

I used to have a Glock 35 .40 S&W years ago. Chamber of that pistol had pretty much taper. Because of that, brass life was very limited, as .40 S&W case does not have much. We made a special tool similar to this : http://www.midwayusa.com/viewproduct...tnumber=358543 and case life was extended.
However, with match loads (heavy bullet + fast powder) there were some case / firearm breakages.

I was told, Glock had much tapered chambers because of feeding. .40 S&W has very little taper, which makes it more difficult to feed compared to, for example, 9mmx19.

After we got first STI .40 S&W pistols, brass life was extended pretty much. With case head sizing tool, I used my training brass some 15 - 20 times with my first STI Edge. After that, those cases could still be used in Glock couple times.

I would say, (once used) case head diameter just front of the extractor groove should be .427" or less if you are planning to use your cases for a long time. .425" or less would be even better, but pistol needs to be tuned very carefully so it will work.

We need to keep in mind, that many match loads generate clearly more pressure than CIP or SAAMI maximum pressure.

I would say, with factory loads there is no problem if chamber is little loose. But, if you want to reload your brass many times and want to use high pressure loads, loose chamber rear end is a problem.

Just my 2 cents

[Irving]

I took this picture sometime last week to help illustrate what this thread is talking about, in case anyone was confused. Sorry it took so long for me to put it up.

This is a .40 S&W seated in the chamber of the barrel of my Smith & Wesson M&P 40 compact.