Unsupported chambers

older glocks (and a few others)in high pressure calibers (.40 s&w, 10mm, bad reloads, etc..) can cause a case rupture if the feed ramp intrudes and doesnt fully support the case head.

all in all i have never personally witnessed it but have heard of it from the guy that knows a guy.

Even though i wuv Glocks I'll admit they can fire slightly out of battery also which doesn't help with KB's. This Kaboom is notorious to the .40S&W round itself and has happened in glocks,keltecs,berettas,to sigs. The 9mm and .357sig chambers are fully supported though. Ain't seen the .45's.

Maybe many "unsupported" chambers are that way because a jackass with a Dremel thought he would 'polish' the feed ramp. Not every chamber, of course, but just a thought in passing...

I reload .40 from range pickup. I've never had a problem sizing with standard carbide dies. Some folks have problems, but sometimes it's their own brass and they own a substandard pistol. The vast majority of .40S&W pistols don't deform brass more than a standard sizing die is able to resize.

The best advice: Try it yourself. The only things in reloading you know for sure are the ones you prove to yourself. In fact, if you wish you may pay no heed to this advice and choose to believe the rumors and falsehoods instead.

glock versus 1911

I have a gen 3 Glock 35 and I compared the unsupported section of the Glock barrel with my 1911 barrel and the 1911 barrel was much more unsupported. Both barrels are stock. That being said, 45 ACP is much lower pressure than .40 S&W.

I reload for the 45 and have had no problems. Although I have saved my brass, have some 180 gr bullets and now have 40 S&W dies, I have not, reloaded for the Glock and probably won't unless I get an aftermarket barrel.

BTW, my Glock is hyper accurate with 180 gr, but hates 155 gr. Does anyone else have the same experience?

Reloads that use bad cases, and or loads above limits then yes, you will experience a (kb) "kaboom" first hand or worse. Faulty factory ammo can also cause this too. Here are some pics of some of my handguns with ammo seated in the chamber, and it clearly demonstrates differing levels of support from most to least.

Walther P1:



SIG 220:



Beretta M9:



I have NEVER had a problem with any, with any load I have made... Pays to be careful and attentive to what you are doing, and handloading is absolutely as safe or dangerous as you make it.

Glock chamber support -



Left to right - 9mm - 357 Sig - 40S&W - 10mm - 45 ACP

So do most think this is more of just an untrue fable or any validity to this issue of unsupported vs supported?

Click to expand...

The pictures show you that a significant amount of the case head is unsupported. That is the side walls are not surrounded by a ring of steel.

The weakest link in any breech mechanism is the cartridge case. Yield strength on quarter hard brass is about 40,000 psia, with tensile in the range 49 to 59 kpsia. Just measure the wall thickness of the brass, and multiply that pounds/square inch, and you will get the idea that the load a cartridge case can hold is quite limited.

Actions that provide a lot of cartridge support are "stronger" than those that don't.

Take a look at the pictures. If the case has a brass flaw, maybe the pressures are high, maybe the case is thin in that area, that unsupported part of the case head is standing all by itself. Nothing there to keep it from swelling out and rupturing.

Now look at a S&W revolver with a recessed cylinder. S&W used to recess the back of the cylinders so that even the rims were surrounded by a ring of steel. It was overkill, but they wanted to maximize case head support.

Most have hit the mark that the 40 S&W being unsupported is much more of a problem than the 45 acp being so unsupported. This is because the 40 has about twice the pressure as the 45. This is compounded since the 40 S&W case as originally deisgned was from a 10mm case that was shortened. It was quickly found out that 180 gr bullets would not fir seated deeper in that case for the 40 S&W. A new case was made. This case had to lose some material around the base to accomodate the 180 gr boolets. This is right where the 40 case is unsupported, and hence the problem. I think also that most people reloading the 45 acp are not loading them hot as a rule but opt for lower power target loads. On the other hand people, like me, reloading the 40 are more likely to keep the pressures up to maintain major power factors for competition shooting.

As far as I have ever seen the KB issue is another beast. Not to be confused with a case that blows out from being unsupported. The only cases I have had blow out were factory cases in a Glock factory barrel. Even loading hot rounds, way hotter than needed to make major, I have never had a case bulge in my KKM barrel in the Glock.

The 1911 Colt has an unsupported chamber, and probably way more reloads have been put through them over the years then any other gun.

Without any problems, unless a shade-tree mechanic with a Dremel made it more unsupported.
Or some misguided reloader tried to make a Magnum out of it.

But the thing is, the .45 ACP is a low pressure round.

When you get to the hotter stuff like 9mm, 10,mm, .40 S&W, .38 Super, and others, supported chambers are very desirable, but not totally necessary if you stay within reloading guidelines for pressure tested loads.

Here is an unsupported chamber (P3AT) with a sectioned .380 ACP case in it.


Again, perfectly safe with normal loads.

rcmodel

Even with 9mm rounds I load with 129 grain cast clocked at 1170 fps, many of the fired cases fully seat into my M9's unsupported chamber by gravity alone... Can't be much "guppy belly" going on or this would not happen.

Seems something would really have to push things way outa whack in order to blow out a sound 9mm case in the vast majority of pistols, and demonstrates clearly to me just what a tough little sucker a quality 9mm case is.

I measure the chamber support from the breech face and compare that to the thickness of the case web.
The difference is the amount of thin unsupported case wall.

The best technique I have found to measure the case support is to:
1) Remove the barrel from the pistol
2) Put a case into the chamber
3) Scribe a line [with a needle] on the case that is a trace of the outline of the feed ramp.
4) Under magnification, hold dial calipers next to the scribed line and end of case head.

The best technique I have found for measuring the web thickness is to:
1) Cut a slit in the case head with a Dremel cut off wheel.
2) Cut a slit in the side of the case so a piece will then fall out.
3) Under magnification, hold dial calipers next to the cross sectioned case head.
4) Put the case head where you can find it, with other cross sectioned case heads, so you don't have to do that again later.

The reason the Dremel cut off tool is used, is because the grinder will smear brass and give false readings on web thickness.


Some case head web thickness measurements:
1) 9mm .160"
2) 32acp .150"
3) 380 .170"
4) 7.62x25mm .185"
5) 10mm .180"
6) 40sw .180"
7) 45acp .180"

Here are some 9mm case supports:
Kel-tec P11 .180"
Glock 19 .180"
Beretta 92S .163"
Tokarev .160"

Here are some 45acp case supports:
Colt 1911 Commander .225"
Para Ordnance P10 .234"
Patriot .180"

Do the 9mm case supports make any real difference?
No, +P+++++++++++++++++++++++++ is ok in any of them for case support, recoil is something else. Primer piercing is something else. If the thin unsupported case wall is .015" thick and it only bridges a .003" gap, it is not easy to blow bubbles in brass.

Do the 45acp supports make any real difference?
Yes, case bulges in a work up are a pre cursor to a case blow out.
Two of those pistols will never even make it to 45 Super in a work up without case bulges stopping the process.

40sw and 10mm are a mess for case support in old Glocks.

Left is Stock Gen3 Glock G23 Barrel
Right is a Lone Wolf Dist. (LWD)
I marked the Cases with Red Sharpie to ease Viewing. Notice the Ramp angle Changes to add support.
The LWD Chamber is .004" Tighter then the Stock Chamber as Measured with my Dial Calipers.
I have no Feeding issues with the LWD Barrel But when I carry I have the Factory Barrel installed.
I shoot Lead,that is why I bought a LWD Barrel.

'Nitro

I've heard of issues with GLOCKs, but I have never experienced a problem. I have shot over 100,000 reloads though my 9mm and .40 GLOCKs- no kb yet. I had a Taurus 9mm blow up in my hand twice after a DIY gunsmith (a friend of mine) decided to "clean up the feed ramp" on his gun and wanted me to try it out. First time it was because of the steel that he ground away. Then he replaced the barrel, asked me to try it out "now" and it blew up again- this time because it was loaded with reloads that had been fired out of the gun prior to the barrel replacement. "I figured that since the full length sizer squished the bubble back in, the case would still work okay" he says...:banghead:

I reload for a Glock 23 and 27 in 40 S&W and have not had any problems. I stay mostly in the middle of the load data.
I use JHP's or plated JHP's in 165gr or 180gr and Longshot powder.
I have shot around 2,000 reloads thru both.