Glock and Kaboom

**Armed Preacher** · 21-09-2008, 16:53

I've seen a few Glock KB's and had a spectacular one myself. I'm interested in finding out what the opinions are regarding the apparent Glock issue with KB.
Before we go on, it must be understood that there is a difference between a case rupture and a Kaboom.
A case rupture is when the case bursts close to the head in the generally unsupported area and a KB is when the gun blows up. I'm not interested in case rupturing as this is indicative of a weak or stressed case in the web area. and is not indicative of a 'faulty' firearm.

**Corné** · 21-09-2008, 18:17

Question: Which Glock's (i.e. caliber) is more prone to go kaboom?

Yes, case rapture is something different but I am not sure if a case rapture also contributes to this.

See the following link:-

http://www.thegunzone.com/glock/glock-kb-faq.html

**ikor** · 21-09-2008, 18:43

While ultimate chamber pressure is similar in both the 9mm and the .40, if you drew out the 'time-pressure spike' for both on a sheet of graph paper, you would find that the 9mm's is more of a gradual build up of pressure than the .40's. In fact, full .40 caliber loads spike max pressures so quickly that when graphed out, the line goes almost straiht up as soon as the cartridge is fired. The .357 Sig is similar to the .40 but not quite so dramatic. In many ways, most factory loads for .40 are 'max' loads, pressure wise since there are no old .40 caliber pistols out there.

As we know, bullet 'set back' can and will increase pressures dramatically. My personal belief...but I have no statistics to back it up...is that, given the millions of trouble free .40 rounds fired just by US law officers yearly, once in a great while one will allow the bullet to sat back in the case upon feeding and when that happens...KB. The Glock was rushed to market in .40, beating even the S&W guns (and they designed the cartridge) and was built on the 9mm frame. As big a Glock fan as I am, I believe the G22 / 23 's have only a small safety margiin for overpressure loads in this caliber because when they happen the max pressure is reached so quickly compared to anything else except the .357Sig...and in comparison there are far fewer of them than .40s out there.In fact, this pressure issue is one reason the FBI wanted to stay with the reduced 10mm loads rather than switch to the .40 years ago..

Reloads are so variable they cannot be factored into the .40 caliber KBs, but in my experience they are even more likely to have problems than factory new ammunition, and many have happened with reloaded rounds. There have also been other KBs with other calibers, makes and models, but no doubt the .40 Glocks have been involved in more than most.

**Corné** · 21-09-2008, 21:33

Interesting about the pressure graphs time lines. I know that they are both ( 9 and 40 ) very similar in pressure but did not know that this aspect differs that much. With local powders I reload with MP200 and prefer to remain cautious (9mm) and I have a very similar concern with going to faster burning powders like MS200 and then S121 and the time line issue regarding pressure. I do think that this makes sense.

I also agree with the point that the 40's in Glock are converted 9mm and it would seem that (and not only in Glock) this is a potential problem. A design that is from scratch a 40 seem to be 'better' that a converted design as you then take the dynamics of the cartridge in consideration for your planning.

Because it seems that the 40's are more prone to the KB, I was thinking that the 357SIG would suffer the same fate especially as its pressure is slightly higher that the 40 but if the pressure time line is different, it would make sense that it would be less vulnerable to this.

**Corné** · 21-09-2008, 21:42

Ikor,

Do you maybe have some of these graphs available as I would like to see them?

**Armed Preacher** · 21-09-2008, 22:05

An interesting article to read about bullet setback and KB
www.greent.com/40Page/ammo/40/180gr.htm

**Corné** · 21-09-2008, 22:29

Armed Preacher,

What I do not understand is that they say the 'web' area of the case gets weakand with reloading. The way I understand it is that straight walled cases like 9mm, 40SW, 45ACP and all the others tend to get thicker at the bottom part as the brass flows back each time the case is used. The case in actual fact becomes shorter and thinner at the front. Cracks normally appear from the front or the mid section. My experience is also (with 9mm and I would assume the same for 40) that the reloads that I discard with case gauging, is a 'bulge' at the back with what looks like a thickening of the brass due to this issue. Yes the bulge is / can also be because the resizing die does not cover the case fully and a portion thus remains unsized, which could cause weakening as the brass is stretched out.

**Geoff Carter** · 21-09-2008, 22:37

Corne,

The 9mmP is not a straight wall case as it tapers from the head to the case mouth. The 40 S&W is a straight wall case and so is the .45ACP now days but originally it also had a slight taper, which was less than the 9mmP.

**Corné** · 21-09-2008, 22:43

Geoff,

Yes, you are correct and I am wrong...from .381 at the front to .391 at the back. Although I think that the same still applies (?)

**ikor** · 21-09-2008, 22:50

Some more fuel for the fire...read especially the secong blurb on Glock .40s here...

http://www.glockfaq.com/reloading.htm

BTW...I do not pretend to 'know' and Corne, I cannot find those graphs now...could have something to do with all the agencies in the US who buy and use G22 / G23's I suppose...$$$