Supported versus unsupported Chamber

[ThePunisher]

Glocks have unsupported chambers...1911's have supported chambers (correct?). I have been trying to wrap my head around this...does anyone have a layman's explaination of an unsupported chamber and how it works compared to a supported chamber? I almost need a damn diagram...

 

[foxbat]

Glock chambers don't 'support' the base of the cartridge, just above the rim..
If you inspect a case fired in a Glock, apart from the vertical (instead of round) firing pin impression in the primer, the case is usually slightly bulged.
A case fired in a typical 1911 doesn't have the 'tell-tale' bulge.
The significance of this is controversial...
The Glock is designed to digest just about whatever ammo you offer it...1911's can be notoriously 'fussy' about certain ammo..i.e. just about anything other than good old 'ball' (round nosed FMJ) ammo.
As well, the Glock is more likely to do it's legendary ''Timex... takes a lickin' and keeps on tickin'' because of this more generous chamber design.
This bulging makes reloading cases fired in a Glock less desirable, as they must be full length sized to prevent misfeeds, and are more likely to fail (split) after fewer fire/reload cycles...
That's one of the (main) reasons why the Glock operator manual stresses the inadvisability of using reloads in their guns (more likely to split/fail) and infact, using reloads in a Glock voids the warranty...(of course, other manufacturers mandate the same warnings) but it is more of an issue because of the unsupported chamber.
Many experience shooters routinely use reloads in their Glocks without issues, citing it to be a theoretical concern only.
If you reload brass fired in Glocks, as a lot of range brass can be, it is advisable to use one of the Lee factory crimp dies as these usually make sure the cases will feed in most chambers.
It's also the reason that many experienced shooters will case guage ALL of their match ammo prior to use...saves those embarrassing 'terminal jams'
at a critical moment...(Ahem, don't ask me how I know!)

 

[Canuck223]

Glocks have unsupported chambers...1911's have supported chambers (correct?). I have been trying to wrap my head around this...does anyone have a layman's explaination of an unsupported chamber and how it works compared to a supported chamber? I almost need a damn diagram...

Just pop out the barrel, and drop in a round. How much brass do you see ahead of the extractor groove?

Old style Colt's didn't have a supported barrel. They had a feed ramp milled into the frame, and a scallop cut out of the bottom edge of the chamber mouth. Many shooters would extend and continue the scallop from the 3 o'clock to the 9 o'clock possition to feed semi-wadcutters.

The newer ramped barrels eliminated much of the need.

 

[capp325]

Check out the Glock Kaboom page. It illustrates the potential problems with unsupported chambers quite well.

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

Glock's unsupported chamber is essentially an engineering cop out. There are plenty of well-engineered, modern guns with fully supported chambers (i.e. HK, SIG, etc.) that provide extremely reliable feeding. Instead of investing in R&D and properly designing the chamber area, Glock figured they’d just let the case hang above the feedramp. Glock fans will probably hate me for saying this, but the unsupported chamber is one reason I’ve always considered Glock a poorly engineered firearm. As many other manufacturers have demonstrated, partially supported chambers are not necessary for reliable feeding.

 

[ThePunisher]

Well that cleared that up...I knew it wasn't too complicated, just couldn't get my head around it. Funny, I know a few people that reload for Glock's and they never give it a second thought, but after reading that article, apparently it can be a really big issue with them.
Thanks for the help and info

 

[Musky Hunter]

bah...i have seen no Glocks KB but have seen a few 1911s.....It is all user error...

Check out the Glock Kaboom page. It illustrates the potential problems with unsupported chambers quite well.

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

Glock's unsupported chamber is essentially an engineering cop out. There are plenty of well-engineered, modern guns with fully supported chambers (i.e. HK, SIG, etc.) that provide extremely reliable feeding. Instead of investing in R&D and properly designing the chamber area, Glock figured they’d just let the case hang above the feedramp. Glock fans will probably hate me for saying this, but the unsupported chamber is one reason I’ve always considered Glock a poorly engineered firearm. As many other manufacturers have demonstrated, partially supported chambers are not necessary for reliable feeding.

 

[capp325]

bah...i have seen no Glocks KB but have seen a few 1911s.....It is all user error...

Any gun can have a kaboom, no doubt about that. It's just that the Glock design increases the probability (same with older 1911's). If you’re using factory ammo you’d probably be aright but if you reload previously fired (and therefore weakened) brass you can run into problems.

 

[Janeau]

Many users disregard safe practice and use 9 mm major ammo which is way over pressure standard for that cartridge. Thereafter if you experience a failure with factory ammo after using previously hot rounds, the overstress of hot reload-read overpressure rounds is the main factor in KB. A gun will not do a KB by itself: it need pressure -a good dose of it - an overpressure.

We shot our guns today more than ever (more rounds- not rare to see gun with 50,000 rounds +)) and metal fatigue due to frequent max pressure load is also to be considered.

Ammo has evolved and 9 mm is even reloaded by factory to maximum and over maximum (9MM +P+) over the standard pressure for that cartridge.
KB on target gun, at low velocity almost if ever happens or happened. IPSC rules and the quest of gaining an advantage by making major by the shooters is a problem created by shooter-reloader, factory ammo maker and competitor.

KB in .45 ACP is almost non existent (low pressure round), but all hot rodded cartridge and guns firing them suffer: .38 Super (modern), .40 and now the 9 mm.

KB start with the shooter and what he have put through his gun. Just watching load being circulated on CGN and some Internet forum and you will understand what I mean.
For those who reload, stay within reloading manual load, and remember that not because a load is listed at maximum that your gun will not show an overpressure before you reach the maximum load published. Too may use bullet not listed in any manual and just assume that they are safe to be pushed to the max load published because they are of the same type of bullet. Bullet brand do vary dimensionally, plated bullet leave more copper in a barrel and more cleaning is needed than most FMJ.

Return to safe load and reloading practice, use standard or target ammo, and your chance of being a victim will be reduced to zero or almost zero.

And my last remark : the Glock unsupported chamber leave less case head exposure than most unsupported 1911, CZ, Luger P08 and other great gun chambered for this round. Supported chamber were invented to allow guns to contain case failure; this were mandated by sport like IPSC which required hot load to make major - re : the .38 super which had a weak case in it's original form ( same as his short brother the, .38 ACP )

I blame the sport requirements, the unsafe reloading practice, maintenance practice, ultimately and definitely the shooter for KB.

 

[capp325]

Supported chamber were invented to allow guns to contain case failure; this were mandated by sport like IPSC which required hot load to make major - re : the .38 super which had a weak case in it's original form ( same as his short brother the, .38 ACP )

I blame the sport requirements, the unsafe reloading practice, maintenance practice, ultimately and definitely the shooter for KB.

Janeau, I wasn't aware that guns like H&K USP, SIG P226, Steyr M40 and Springfield XD were specifically designed for IPSC.

The guns that you listed were invented almost a century ago. In addition to having unsupported chambers, they were also made of much lower quality than modern guns, had tiny sights and no corrosion resistant finishes. All of those characteristics would be unacceptable in a modern combat pistol.

Just because those old guns had unsupported chambers does not mean that modern guns should duplicate their shortcomings when you can make a perfectly reliable gun with a fully supported chamber.