Wednesday, November 4, 2009


(sorta 2 posts in one)

Does anyone know of a catastrophic failure, where a modern gun blew up in someone's hand that DOESN'T include a variation of the phrase "so I was taking my reloads to the range to try them out..."

You see it on the blogs and in the forums. A picture of a revolvers cylinder blow apart, or the chamber of semi-auto bulging out in an ugly matter with a deformed mag well adding to their woes. They always seem to have a hot load in there. Even squib problems don't have catastrophic failures, that I've seen. I even remember a Ruger revolver with MULTIPLE bullets stuck in the barrel because the first was a squib. The barrel looked fine, except they sliced it down the middle to show the problem. If they had dug out the lead it might have worked fine.

And I've seen OLD photos of failed 1911. From 80 years ago. That might be a metallurgy limitation.

But has anyone confirmed a failed modern gun blowing up using (presumably faulty) modern factory ammo? (there are a precious few.)

Of course you could get a blowed up and ruined gun with an out of battery failure. The round isn't seated and supported in the chamber and the bolt isn't fully locked when it goes up. That's more a fault of the gun and not a ammo problem. But you DO see very broken guns when it happens. So that counts, I guess, and could apply to just about any semi-auto.

Bad things could happen with a revolver that is used enough that it doesn't lock up tight and isn't centered on the barrel when the hammer comes down.

But to get really spectacular failure, where your handgun doesn it's best impression of a hand grenade, you need to reload. Though I have been looking for exceptions to that rule.

~~~ !!! ~~~

There is one way to get factory ammo to ruin your day and destroy a gun. A way I had heard of, but didn't fully understand until this post, and then only because I stumbled over it in the research. And it's a common thing I DO. I, obviously, need to address this danger.

It's called bullet set-back or setback.

You go to the range with your CCW for practice. You don't want to shoot your expensive self-defense ammo, so you remove your magazine and the chambered round and use ball ammo. After the session is over you replace the self-defense round that was in the pipe into your magazine and then reload the mag and set your gun to Condition One, with a round ready to go in the chamber. Next month you do the same thing again at the range. And the next month. After a year, that one bullet has been replaced back in the mag and shoved back into your gun's chamber TWELVE times. More if you go to the range more. Presumably you haven't shot at bad guys in the intervening year. I have to do this procedure at home on range day because I live in Maryland, but the principle is the same

Why is this a problem? Well, the feed ramp on your pistol pushes a little bit against the front of your first bullet. This may cause the bullet to bet shoved a little further back into the brass cartridge full of powder. This may compact the powder into a tighter space and it might jam that bullet into the brass so it sticks a little harder. When you go to shoot the round at a bad guy the compressed powder and/or stuck bullet could cause an excess amount of pressure that can burst the chamber.

This is the definition of BAD! Bullet setback of perfectly fine factory ammo fired out of a modern firearm can destroy a gun and maybe hurt you.

And I was blissfully unaware of this in anything but briefest glimpse of the theory reading in the margins on the intarwebz.

Then I saw reports of police ranges where it happened, and dug around a bit and learned what I just told you.

If you keep reloading that top round in the mag into your semi-auto it can explode. All because of something you did that you didn't have to do.

Apparently, some guns are worse for causing this situation than others. Some ammos are too. Which ammo? My ammo? Which guns? Any of mine? I don't know!

Why didn't I hear about this from all the bloggers I read? I may have heard Tam mention it but didn't bring two and two together. Why didn't my CCW trainer mention this? Why does this happen to cops, presumably they have had a few hours of firearms training. I know infantry type people and they never mention it, but they tend to not unload reload as much, maybe. I had to dig around internet gun failure reports for a while to learn about this type of problem.

What of the New Saturnian Thunderclap neophyte shooter that was getting into guns back in 1975? With fewer books and no internet and learning from his grandfather in the passed-down knowledge tradition we all used to learn from would leave him woefully unprepared.

I'm still learning about setback, and you should educate yourself, too, if this is news to you. Yes, it seems that reloads tend to do this setback thing more than factory ammo, going back to my original point of 'do you know a gun exploding using factory ammo' at the beginning of this post. But factory ammo is not immune. Most of the examples I see are Glocks, but 1911s are not immune, either. Nor is whatever you are shooting.

I even see the failure referred to as 'KB' or 'kB'. I guess that stands for KABOOM! (Though one form of kB may be Glock specific and refer to a case failure near the base. The effect from setback or case failure for the user are the same. Ow.)

And now it has scared the hell out of me.

I don't know yet how I am going to change my procedure, other than shooting off self-defense ammo more frequently and inspecting ammo before putting it back into battery for carry.

One thing I might do is have a box of the same brand self-defense ammo and when I strip out a round replacing it with a brand new round each time.

Ideally, you just put the round in a magazine one, then fire it down range, never putting a round back in the mag. Ideally.

Setback can't be TOO bad or it would happen more often on just that one time the bullet tip touches the feed ramp on its way into the chamber then down range.

Some brass cases are crimped around a groove or ridge in the bullet when made at the factory or at home. Is my ammo crimped like this? I don't know. Can reloading weaken the brass so this crimp fails to hold bullet where it belongs? Probably.

This can happen with revolvers, too. Another thing I think I remember Tam mentioning in conjunction with uncrimped .45 ACP brass in a 625 style revolver. Then the bullet can move forward out of the case as well as back. And forward or back, that can't be a good thing.


Top of the Chain said...

Tam has mentioned it in passing in the last three or four months. Maybe in a post about a range trip.

New Jovian Thunderbolt said...

That's teh entry I remember. But she didn't elaborate!

It's like listening to news on the radio, and havingit fade out about some military... test... experime...

And when the sound comes back it's "but if you take that simple precaution for the duration your eyeballs won't melt ooze out of their sockets. That's the News! Goodnight."

Ian Argent said...

I recall her (or someone) mentioning it enough that this newbie shooter who doesn't (and can't legally) CCW asked if the self-defense ammo was so expensive that shooting off a magazine of it as the first mag was too expensive to use as a prophylactic against KB (not in those words).

Disclaimer - I shoot whatever I can get ahold of cheap, no more often than once a month (though when I do go to the range I tend to run through a fair amount of ammo).

Anonymous said...

I've known about this problem for a long time but never really mentioned it because it's so easy to prevent.

When you are reloading your gun after a range trip or after having had to unload it for storage, why do you go through the hassle of inserting a mag, jacking the action, pulling the mag, topping off the mag, and reinserting it?

Or, alternatively, why do you carry a mag that is one round down?

It's very simple to reload quickly to maximum capacity and never have to worry about pushing the bullet back with repeated loadings:

Before inserting the mag, lock the slide open. Drop the loose round into the chamber. Release the slide. Engage the safety. Insert and lock the full magazine.

Presto. Fully loaded gun and you didn't set your bullet back.

Isn't that how everyone does it?

New Jovian Thunderbolt said...

That's not how I do it because I 'learned' long ago that that is 'bad' and breaks the extractor and other things.

Anonymous said...

That's new to me...'course I could just be living under a rock.

But I've been doing it that way on various and sundry guns, some of which have had thousands of rounds fired through them, for over ten years now...since I first started carrying a firearm defensively...and I've never had a problem with it.

Not exactly scientific so your mileage may vary.

I don't see how the forces exerted that way would be significantly different than the forces exerted when the action is cycling normally normally.

Anonymous said...

Sorry for the stutter.

Editing artifact.

GunGeek said...

It's not just repeated loading of a round that can cause setback. If you get a FTE and the next round comes slamming up against the fired case it can also shove the bullet back into the case.

I had that happen with some factory 180gr 40S&W ammo and it pushed the bullet well back into the case. Using 180gr in 40S&W is a wee bit on the risky side all by itself, primarily because of the heightened consequences of setback with that combination. Fortunately, I checked the condition of the round before allowing it to load.

It could have been a very interesting day, indeed.

New Jovian Thunderbolt said...

The theory I was told about inserting a round manually, (not being an expert, I don't know) is that out of the magazine the rim slide up under the hook of the extractor on its way to battery. Dropping a slide on a manually inserted round makes the extractor spring up and over the rim. When that works. I've had trainers and the internet warn me against doing anything but letting it load from the magazine.

Perhaps more people could chime in.

TJP said...

"Why didn't I hear about this from all the bloggers I read?"

Probably because setback is very rare. If you're chambering the same round 12 times, you probably aren't going to the range and expending your defense ammo on a regular basis. Just shoot once a week, cycle magazines, and don't worry about it.

Well-made ammo shouldn't experience setback. It's one of the things I test in my reloads by measuring COAL on a test round while cycling it. Being an alumni of the Big Bore School, I'm used to putting a serious crimp on the bullet, even a taper-crimp on rimless pistol cartridges. The wimpy spring in my pistol can't compare to the force applied by my press ram, and believe me, the nose will distort, the bullet jacket will blister and the case will go accordion before a good crimp lets go.

There are downsides to heavy crimps, but I'll be damned if I can tell the difference at 30 yards, and anyway, people who crimp like nancy-boys always run into ignition problems with slower propellants.

There are sui generis conditions of the available cartridges, and the best way to learn is to roll your own.

Arthur said...

A bullet doesn't have to compress the powder to cause excess pressures it just has to reduce the starting volume of the case. I had cast some 45 bullets out of a 230gr mold using a high tin, very light alloy. The bullets came out at around 185gr. When I loaded them I used a light starting charge for the weight - 185gr. WRONG choice. Instead of being a light target load they were serious thumpers. The physical size of the bullet reduced the starting volume of the case and altered the burn rate of the powder.

"I've had trainers and the internet warn me against doing anything but letting it load from the magazine. " Depending on the gun and extractor, dropping the slide on a loaded round can rapidly damage or de-tension the exractor. The extractor on my first Sig P220 is limp as a wet noodle from smacking into the rim lots of times before I knew better.

Arthur said...

Ah, I forgot to add, I always check the space between the base of a loaded round and the top of the powder charge to make sure I don't compress the powder, and there was still room left over on my light alloy bullets.

Mike W. said...

I seem to remember at least one case of a KB with a .22 pistol (Beretta Neos I think) which was the result of a double charged factory round.

Then there's instanaces of Walther P22's cracking slides.

BTW - An OOB discharge could be the fault of ammo and not the gun, if the issue is an out of spec round.

I try not to chamber the same round more than a handful of times, particularly with my +P 9mm, 357 SIG, or .40S&W rounds.

Rick R. said...

One trick (rough rule of thumb ONLY -- YMMMV) is to ride the slide half shut, then let it slam shut on the (already) chambered round.

This (roughly) duplicates the actual slide closing velocity you would have if the slide had to deal with the drag of stripping the round out of the magazine.

It's an old Garand match technique. Works great with just about any autoloader.

But the suggestion that you simply donate the chambered JHP as the first round of range practice has merits too. At least you'll EVENTUALLY cycle through your defensive ammo supply.

Also remember -- it's double the stress on the top round if you wait to clean your weapon. Because
you'll be cycling that round out AGAIN when you get home, as you clear it to clean it. (And honestly, there's no FUNCTIONAL reason to clean your weapon at the range for firing off 100 or so rounds. It could wait until you get home, and the gun will work just fine if Der Tag hits on the way home. If your primary carry gun won't shoot unless it's surgically clean, you're carrying the wrong gun.)

Of course, if you bring a revolver to the range, there's no set back problem incurred by dumping your defensive loads out, and then reloading them at the end of the session. And who couldn't use another 3"-4" K-frame wheelgun?