Explain this malfunction


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marb4
May 26, 2011, 12:26 PM
I'm curious about a specific type of malfunction that I've had occur a few times in the past with a couple of different auto-loading pistols. Just for the sake of educating myself I'm hoping someone can give some insight as to how or why this type of malfunction occurs. Here goes...

After the round fires the slide cycles completely back (cocks hammer and picks up next round in mag). The problems is that the spent case has remained fully in the chamber (not stovepiped or "jammed" in some other way). The few times this has happened to me the spent case was easily removed and didn't seem stuck in any way. Obviously the extractor has come off the case at some point but it seems that even if the extractor wasn't present at all the case should still come out of the chamber due to the force of the firing alone (it may stovepipe but it should still come out).

How is it that the case remains in the chamber?
How does the slide cycle if the spent case isn't pushing it?
Does this malfunction have a specific name?

I'd appreciate any thoughts you might have.

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Vern Humphrey
May 26, 2011, 01:00 PM
How is it that the case remains in the chamber?
It usually doesn't. What happens is the case comes partially out, then is pushed back into the chamber either by the pistol attempting to chamber the next round, or by the slide closing if there is no next round.
How does the slide cycle if the spent case isn't pushing it?
In a recoil-operated pistol, the pressure is so low at unlocking that the case will not be expelled by gas pressure.
Does this malfunction have a specific name?
Failure to extract.

You need to check your extractor -- what sort of pistols are you talking about?

marb4
May 26, 2011, 01:28 PM
The two pistols this has happened on are an old Browning Hi Power and a new Beretta 92FS. On the Hi Power it will happen once in a while using the Blazer aluminum case ammo. On the Beretta (which has around 500 rounds through it) it has only happened once using WalMart Federal brass rounds. My wife (who is not an experienced shooter) was shooting the Beretta when it happened so I'm not sure if in this case it may have had something to do with the way she was gripping the pistol. I've performend an extractor test on both guns and they seem fine. (remove the slide, place an unfired round under the extractor and shake) It took a lot of heavy shaking to make the round come off on both pistols.

Even if there was no extractor shouldn't the spent case at least fully come out of the chamber?

These aren't major issues with these guns. Just something curious. Always trying to learn.

Vern Humphrey
May 26, 2011, 01:32 PM
On the Hi Power it will happen once in a while using the Blazer aluminum case ammo
Blazer ammo has more friction when expanded -- but a new extractor should cure the problem.

Even if there was no extractor shouldn't the spent case at least fully come out of the chamber?
Nope, because:

1. Pressure is almost zero when unlocking is complete, and

2. The next round in the magazine pushes the fired case back in when the gun attempts to chamber it.

KodiakBeer
May 26, 2011, 01:33 PM
It's easy to test a BHP extractor. Remove the slide and slip an empty case up under the extractor. It should be held firmly against the breech face - and I mean firmly as in waving the slide around won't dislodge the case. If it isn't held firmly, it's time to replace that $3 spring.

Dobe
May 26, 2011, 01:44 PM
It could be the extractor, ejector, or even the recoil spring being too heavy or out of spec. The later happened in one of my HK P30s.

Marb4, what make and model of handguns are you talking about?

edit: After the round fires the slide cycles completely back (cocks hammer and picks up next round in mag). The problems is that the spent case has remained fully in the chamber (not stovepiped or "jammed" in some other way). After re-reading this, I tend to think your ammo is under powered. In many autos, assuming at least std pressure ammo, the next round in the mag would have jammed against the empty brass as it was being shoved back into the chamber. The effect you experienced is also the same as you would experience with a recoil spring, which is too heavy for the gun.
In other words, if the slide had been pushed all the way to the rear, it would have picked up a round from the mag on its way into battery.

marb4
May 26, 2011, 02:28 PM
"In many autos, assuming at least std pressure ammo, the next round in the mag would have jammed against the empty brass as it was being shoved back into the chamber."

This is exactly what happened with both pistols (Browning Hi Power / Beretta92FS)

It's easy to test a BHP extractor. Remove the slide and slip an empty case up under the extractor. It should be held firmly against the breech face - and I mean firmly as in waving the slide around won't dislodge the case. If it isn't held firmly, it's time to replace that $3 spring.

An unfired round on the Hi Power is almost impossible to shake off. The round on the Beretta slide will come off but you have to shake it pretty hard. Again its only happened once with this gun so maybe it was a one time thing.

See if I have this right. The round fires. The barrel locks but the slide begins to move back. Or does the barrel begin to move back with the slide and then lock?

GLOOB
May 26, 2011, 02:35 PM
Obviously the extractor has come off the case at some point but it seems that even if the extractor wasn't present at all the case should still come out of the chamber due to the force of the firing alone (it may stovepipe but it should still come out).
True in a low pressure blowback pistol. Some will function even without an extractor. But your pistols are high pressure locked breech guns.

Barrel and slide are locked to begin with.

Round fires.

Momentum is imparted onto the barrel and slide. They are propelled backwards as a unit.

Barrel unlocks on the way back and hits a stop. Slide continues on by its own, carried on by inertia.

Extractor is connected to the slide. It rips out the empty brass.

At this point, peak pressure is over. But the brass is still expanded against the chamber walls, making it stick and making the extractor work a bit. When the barrel stops, the extractor has to yank the brass from dead-stuck to slide velocity, instantly.

Extractor, ammo, and recoil spring work together to produce this failure. One or more of the three might be beyond its limits. Extractor might be weak. Ammo might be hot. Recoil spring might be weak, allowing the gun to unlock early, while the brass is still stuck hard against the chamber.

Once all the pressure is gone and the brass has had time to contract, the case slides out more easily, as you have observed.

Vern Humphrey
May 26, 2011, 02:39 PM
The barrel locks but the slide begins to move back. Or does the barrel begin to move back with the slide and then lock?
The barrel and slide move backward together for a short distance. The barrel unlocks and comes to a stop, while the slide continues rearward by inertia (not by gas pressure.)

If the extractor is functioning properly, the case continues to the rear with the slide, held by the extractor, until it is kicked aside by the ejector.

In your gun, the case is not being extracted. It may move back out of the chamber a bit, but not much, since pressure is so low by the time the barrel unlocks. In any case, the next round will shove it back into the chamber as the counter-recoilling slide pushes it forward.

marb4
May 26, 2011, 02:46 PM
Thanks. This is exactly the info I was looking for. It makes sense now why the case would stay in the chamber if the extractor slipped off. I shoot a lot of rimfire auto loading pistols where the barrel is fixed so my mind was assuming that the sequence would be the same with most centerfire. This helps me understand what's going on when I squeeze the trigger on my centerfire pistols.

Apocalypse-Now
May 26, 2011, 05:28 PM
the empty shell indeed left the chamber--initially. when it was not ejected, the slide sent it back into the chamber.

it's usually either a bad extractor or ejector :)

marb4
May 26, 2011, 06:36 PM
Just for kicks I removed the extractor from the Beretta and was amazed at the amount of sludge and crud underneath. I can't believe that its only malfunctioned once. Anyway, giving it a good cleaning. Should eliminate any problem that may have been starting.

Vern Humphrey
May 26, 2011, 06:46 PM
Sounds like you're going in the right direction, then.

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