unsupported barrels

[jjavedas]

Is Glock the only pistol that comes w/an unsupported barrel,and whats the advantage.
Thanks jj

[Fishbed77]

I assume you mean "unsupported chamber?"

Many pistol designs don't fully support the chamber for various reasons (reliable feeding and extraction, parts commonality, etc.)

Earlier generation .40SW Glock pistols gained some notoriety for their lack of full chamber support, even though almost all failures were due to reloads or otherwise out-of-spec ammunition.

[74A95]

Traditional 1911s have unsupported barrel chambers. Only ramped barrels offer better support in these guns, and ramped barrels in 1911s are a minority of factory guns.

Few pistols require a fully supported chamber - where the case is supported all the way to the extractor groove. Cases generally have brass thick enough at the head to withstand the expected pressure. Even many 'supported' chambers don't offer support all the way up to the extractor groove and leave some of the head exposed. for example: https://detroitammoco.com/unsupported-chambers/

[44 AMP]

Is Glock the only pistol that comes w/an unsupported barrel,and whats the advantage.

Glock isn't the only one, nearly everyone does it to a degree, and it usually is a non-issue. However, Glock relieves more of the chamber than most, and got famous for it, and it has caused issues in certain cases.

Why do they do it? What's the advantage?? Feeding reliability.

Essentially, what the gun is doing is trying to shove a straight cylinder, or very slightly tapered cylinder, with a dull point (or no point) into a steel hole that is only a couple thousandths of an inch larger than the cartridge, doing it very fast, and from a slight angle. Making the chamber bigger at the back (removing more metal, on the bottom of the chamber) means the cartridge has a bigger hole (taller) to enter, which means it has more "room to make the turn" in order to be lined up with the bore to enter the chamber all the way.

As stated, the solid brass head of the case doesn't need the support of the barrel. It is strong enough to handle the pressure, so cases don't need to be supported all the way to the extractor groove. Regular barrels support the case down to the solid head of the case (which begins a short distance above the extractor groove).

Glock, and some few others have chambers where the support ends a short distance ABOVE the solid head, leaving a portion of the thin case wall unsupported.

This means more room (clearance) for the round to enter, and means they feed more reliably. BUT, there's no free lunch. The unsupported case wall stretches under the pressure of firing, It BULGES out. This is not normally a problem when firing a case ONCE.

Glock doesn't care if the case bulges, from their point of view, it only has to work once. There are a number of firearms that are not "reloader friendly" the way they treat the brass. Most are designs intended for military use. Doesn't matter what happens to the case, bulge, stretch, get banged up or even ripped rims as long as it doesn't rupture in the chamber, and gets cleanly ejected after firing.

The problem is that when the stars line up, you get a situation where the brass doesn't just bulge where the thin wall is unsupported, it ruptures. This releases the chamber pressure back at you. KA-BOOM!!

Brand A ammo fired in an unsupported chamber may be perfect fine (once) bulging, but maintaining its containment of chamber pressure. Brand B might have a slightly thinner case wall (and still be in spec) so that when it bulges, its not quite as strong (at the bulge) as brand A, and so Brand B tears open (ruptures). And, both brand A and brand B can work fine in a gun that does not have its chamber relieved as much as Glock does.

Glock became famous for this happening with their early production runs of .40S&W. Apparently what ever ammo they used during their design testing was "Stronger" than some of the ammo commercially made and sold to the US public, so there were a number of blowouts.

Something did get changed, and I don't know if it was the ammo makers increasing case wall thickness, or GLock deciding that their "perfection" needed to be "adjusted" but the Ka-Boom problem has gone away, pretty much (with factory ammo, anyway ) but the memory of it, lingers still...

[RickB]

I have noticed a trend along the lines of "higher-pressure cartridges need supported chambers", but that's closer to old wives' tale than conventional wisdom.

As noted, 1911s don't generally have supported chambers, and Colt used to make guns chambered in 9x23 WIN, which runs at 55k psi chamber pressure, in an unsupported barrel.

[JohnKSa]

I believe that the 9x23 brass was specifically designed to provide a lot more strength in the areas which are often unsupported in a typical autopistol.

[rock185]

Hello JJ, Supported/unsupported is a relative term. Glock barrels did seem to be throated more extensively than many other manufacturer's barrels, perhaps to achieve Glock's vaunted feed reliability? I can't see any other reason to leave so much unsupported brass hanging out over the feed ramp.

Reference traditional Colt type unramped barrels, that tend to leave more case head unsupported than the ramped type, I've owned a bunch. Generally not a problem, but like some others, I do prefer a ramped barrel for the higher pressure cartridges. This, for both feed reliability, and increased case head support.

I've used unsupported barrels in 9MM, 38 Super, 10MM, etc., and nothing blew up. Bulged, but never blew. The 9X23 Winchester has the strongest case head of any regular semi-auto cartridge I've ever worked with. While it was designed to be safe in Colt type unramped barrels, I've only had the opportunity to use it in pistols with ramped barrels. I like the cartridge in any case, and wish it had been more commercially successful.

[Jim Watson]

I understand that Glock has tightened up their case exposure in later generations. It was never a problem except in .40 cal where they crammed the fatter round into a 9mm action.

The 9x23 Winchester is made of rifle temper brass because Colt was unwilling to go to the steep integral ramp commonly used to contain overloaded .38 Super in raceguns.

An integral ramp barrel, if made steep enough to cover more brass, can limit bullet choice. I had to have my Springfield 9mms recontoured, not just "polished" to handle anything but hardball. Case support is still comparable to other 9mms so I am not giving up anything since I am not overloading to 9mm Major.

[rock185]

J. W., Several years ago I saw a Glock 21 that had Ka-Boomed during a night shoot. Looked like most all the others many of us have seen pictured on the internet, case head blown out, feed ramp bent downward, frame about broken in half, etc. Sometime afterward, I started noticing that, just as you mentioned, later Glock production had better case head support. In the G21 I noticed that later barrels had been "beefed up" I guess one could say, more steel beneath the ramp,etc., as if to strengthen the ramp itself. Glock "Perfection" improved upon. Fortunately, my Glock .40 never Ka-Boomed, but did have a serious malfunction during an incident, when I really really needed it to work.

BTW, My 9mm Springfield with factory ramped barrel had feedway malfunctions with some bullets too. The SA was he only ramped type 9mm or .38 Super barrel I can recall having these type of reliability issues. Probably some dimension, or angle, with the factory SA barrel that was not optimum. I didn't spend a lot of time diagnosing the issue. That particular gun was slated for considerable custom work, and the factory SA barrel was replaced by an aftermarket ramped bull barrel. Flawless reliability with the new barrel.....

[jjavedas]

Hey thanks for all the response,I feel better informed on the subject.learn something new everyday. JJ

[Jim Watson]

Hadn't seen a G21 let go, but it makes sense.
The G21 is to the G20 as the G22 is to the G17; a larger diameter round in a platform designed for a smaller.

[Nathan]

Advantage:
It’s like basketball....it is easier/more reliable to hit a bigger hole.

Disadvantage:
Sometimes you get it wrong and the guns kaboom.
You have lower case life reloading due to the bulge.

[COSteve]

By their very design, all John Browning based semi-auto pistols (read every make currently produced) has some degree of limited case support in the 6 o'clock position due to the feed ramp cut in the bottom of the chamber mouth. That's right, every single semi-auto centerfire pistol made today has less than 100% support at 6 o'clock in the chamber. Some more, some less, but none have fully, 100% supported chambers. If they did, they wouldn't feed reliably.

Early Glocks had very generous chamber dimensions to ensure that they would feed even when muddy. Remember, Glocks were designed as combat pistols for the Austrian Army and it was assumed that they would never see reloaded ammo or other than Austrian Army spec'd ammo. This made it possible that some excess bulging of the cases would occur. In the early 2000s, Glock reduced their chamber sizes somewhat and reduced the size of their feed ramp cuts at 6 o'clock so that the chambers gave more support to the cases. All Glocks made after that have this tightened design.

I've fired thousands of hot 165grn loads in both my 2003 Glock G22 and 2004 Glock G23 over the years and neither produce bulged brass. Further, I've shot my 'nuclear' 10mm loads in my neighbor's stock G20 (my custom G20L has a 6" KKM target barrel with a tight chamber) and even in a his stock Glock, those 'nuclear' level handloads only produce very slight, .002"-.003" bulges in the case. No more so than when hot ammo is fired from any other 10mm platform.