Pressure signs

It seems to me that the process of reading pressure signs in your brass and primers, as they tell us in the loading manuals, can be a bit ambiguous. In this instance however it was rather obvious.

Pressure signs

Too much pressure?

It’s a Glock 40 S&W with a Lone Wolf barrel. The case blew out at the space above the feed ramp on the barrel, where it has less support. The Glock’s extractor was blown away into Kingdom Come, leaving the extractor spring and plunger hanging out. The trigger was blown down and out of the frame. The magazine, damaged but still in one piece, was blown down and out of the frame, breaking the mag catch in two and driving the magazine into the pistol bag he was using as a rest. You can see the outline of the magazine floor plate in powder residue in the fabric, stenciled in powder residue.

Glock kaboom

Where the trigger and mag catch used to be

Magazine impact stencil. Definitely a double stack.

Magazine impact stencil. Definitely a double stack.

The shooter’s right (strong) hand was cut, apparently from the extractor turned projectile. The index finger had a long, narrow blood blister on it, caused by gas pressure escaping between the slide and frame. He was peppered by small bits of brass, from the chest up to the face, leaving little blood spots, but all superficial. He’s perfectly OK, really. Nothing that will leave a permanent scar. Good eye protection saved his sight.

Remnants of trigger and mag catch

Remnants of trigger and mag catch


Internals intact. Finger mostly intact

I was standing immediately to his left and behind, so he was between me and the gun and I apparently wasn’t hit by any fragments. I was taking readings off the chronometer as he was shooting; “Bang”, take a reading, “Bang”, take a reading…”BOOM!”

I felt the concussion all out of proportion for the pistol, as he dropped his head and chucked the pistol onto the shooting table. “That didn’t sound right” I said. Duh. I took a couple seconds for him to reply, as I assume he was internally reeling from the violence of the event, trying assess the extent of its seriousness.

After seeing that he appeared to be OK, we took a close look at the pistol. It’s interesting how the mind perceives things according to context and expectation. I thought the frame had been torn up pretty bad at first, but it turned out that my mind had just made that up. For a moment I had actually seen something that wasn’t. So much for me as an on-the-spot eye witness. Upon close inspection, the frame actually seemed to be fine. It was missing the trigger and mag catch, but otherwise it looked as though it could be reassembled with a few new parts and would function normally.

Disappeared extractor

Disappeared extractor

Slightly over-sized flash hole

Slightly over-sized flash hole

I advised him to have it checked out before using it again. Kudos to Glock and to Lone Wolf though, really– The barrel, slide and frame all seem to have taken the extreme offense without apparent damage. I figure that a Glock barrel, with it’s deeper cuts into the chamber for the feed ramp, might have let more gas into the frame, causing more damage, though that’s just my theory. Certainly there is more case support with the Lone Wolf chamber, and certainly that helped to direct more of the energy out through the barrel.

The gun was locked up in battery after the kaboom. Somehow the striker had been re-cocked over the trigger sear, because I had to use a screw driver to push the trigger bar back so it would let go of the striker before we could remove the slide. I believe the striker was blown back by gas pressure to reset. That seems likely enough, given the looks of the flash hole in the cartridge case. The barrel never unlocked, as the case head flowed out and filled up much of the square space inside the slide near the breech face, effectively “glueing” the barrel and slide together. The web portion of the cartridge case also flowed (extruded) backward and “accordioned” against the case head. It took some surgery with a hammer and punch to extricate the barrel from the slide. The case was completely separated in two, forward of the web, or about midway on the case.

Extruded case

Extruded case

Remainder of case, stuck in chamber

Remainder of case, stuck in chamber

Pretty obviously an over-charge. Though new at it, he said he was well aware of the potential dangers of reloading, and was being extra careful with charge weights. Probably a carefully measured double charge.

He’d gone on quite a bit about how careful he’d been to calibrate the scale and meter the powder and such. That’s all well and good of course, as far as it goes, and this is a concept with which I’d become very familiar in the audio business; it ain’t the equipment, necessarily. It’s the operator. I don’t want to embarrass the man (we ALL fall prey to the over-reliance on equipment and numbers at times, when we should be looking elsewhere for our salvation) but to uphold the concept.

Afterward, I asked him to measure out two of the charges of the CFE Pistol powder he’d been using, and sure enough; a catastrophic double charge fits the little case fairly well. His intended charge was six grains, so he tried 12.7 grains. Though some powder compression would take place upon seating the 180 grain bullet, a double charge is certainly doable. The photos show an empty case, a charged case and a double charged case, plus all three cases seated using his regular die setting. The double plus charged cartridge OAL came out 0.015″ over target; not something you’d notice without a cannelure, necessarily, unless you measured every finished round. Note the only visual clue is a slightly more pronounced pressure ring on the bullet from the seating stem.

Hodgdon lists the max charge of CFE Pistol for a 180 grain bullet in that caliber as 6.5 grains, so yeah; twelve or more is rather too much.

Double charge (left) fits OK

Double charge (left) fits OK

Double charged and seated. Looks fine to me.

Double charged and seated. Looks fine to me.

Something he’d said before we went out shooting came back to me. I’d thought to say something at the time, but the course of the conversation put it out of my mind just then. He’d said that reloading was something he could do after a long, hard day, because it was monotonous. No, Young Grasshpper; one must be fully alert, with full faculties, when assembling ammunition.

The load that blew was part of a batch of the lightest load he’d brought that day (and therefore the most likely to be double charged without noticing). The others, which he’d fired first, all went off nicely, and velocities were right in the ball park for the caliber and loads. The one that blew left a number of fifteen hundred and change on the chronograph, numbers flashing, indicating a probable error. That’s closer to 44 Magnum territory, in a compact polymer pistol! I wouldn’t be surprised if that were close to actual velocity though, considering the effects it had on the launch system.

So it seems you CAN push a 40 Smith, 180, to 1500+ fps from a compact pistol, so long as you don’t mind it blowing the gun apart, turning various piece of the gun and cartridge case into dangerous projectiles, and bloodying you up a bit. Now you know.

I’m sure you’re jumping up and down at this point, yelling at your computer screen with the pertinent question; “But did he HIT the TARGET?”
Yes. Yes he did, and he walked away from it, and so it was a completely successful shot. So there.

He felt foolish, but I told him he should look at it as a gift. He’d gotten a valuable lesson he’ll certainly never forget, no one else was hurt, it wasn’t terribly expensive, AND he kept all of his body parts more or less intact. What more can one ask?


9 thoughts on “Pressure signs

  1. There are a few truisms in gun land—
    1) There are two types of shooters, those who have HAD a negligent (accidental) discharge….and those who will.
    2) There are two types of reloaders, those who HAVE double charged a case, and those who WILL.

    I always recommend that new reloaders find a powder that makes it almost impossible to double charge a case. With .45 ACP it is Trail Boss. You simply can’t get a double charge without intending to do so because it will spill at double normal charges.

    It is tough to do with most rifle cases, but easy in pistols.

    Be safe!

    • Same goes for Unique. 5gr in .45ACP will just over half fill the case. So if you double charge the case it will be overflowing. Good idea to visually inspect the charged cases and maybe even empty and weigh one just to make sure before seating.

  2. PS….An old pilot friend told me that any landing you walk away from is a good landing…..The same goes for double charged cases, if you walk away with all your parts, its a good day!

    • and…It’s a great landing if the aircraft is still reusable.

      Is he crimping his reloads? I ask because the Glock seems to have a nasty tendency to drive the bullet back when it impacts the feed ramp. I’ve measured this even with factory ammo. It moves almost every time.
      With one batch of re-manufactured .40 ammo, it was frightening how much it would move. Also, it would vary depending on who was holding the gun (g27)! The other guy is a very experienced shooter, but mostly shoots full size, steel frame 1911’s. I saw as high as .067″ setback. He got as high as .177″. The odd thing is his kept stopping on the ramp, but that never happened with me. For some reason, the term “limpwristing” comes to mind. I’m not sure how to determine what the actual dynamics are that would give such a difference in results.

  3. Ah, yes, the classic KaBOOM!

    .40 Glock. Your article doesn’t mention a lot of pertinent information.
    How old was the .40 Glock (early versions did NOT have ‘fully supported chambers’, and the pictures suggest that this may have been one of them). I’ve documented classic KaBOOM incidents over the past decade, see:!

    It my very well have NOT been a double-charge. But the article does not document whether the press was a progressive … where it is very difficult to get a double-charge because the shell-holder (or the turret) advances the case from one stage to the next.

    If it is a single-stage press, then one very good way to prevent this is to use loading blocks … where you run a batch of cases through each stage, or a couple of stages, and then after the powder stage you stop and visually inspect every primed & powdered case under a strong overhead light. It’s easy to spot both and uncharged and an over-charged round that way.

    .40 Glocks have been known to blow without the need of a double-charge. This is because the caliber has been loaded ‘hotter’ than usual because the shooter wanted to make “Major Power” in IPSC matches. Often reloaders used very fast-burning powders, so they get pressure-spikes. With unsupported chambers, or with often-reloaded (hence weakened) brass, that can cause exactly the situation which you have described.

    Don’t make the mistake of simply ASSUMING that you have had a double-charge. There are other factors which might cause the exact same consequence without necessarily loaded the cartridge with too much gunpowder.

    The rest is left as an exercise for the student.

    • Did you read the account, or look at the pictures at all?

      I repeat; it’s a Lone Wolf barrel, which has more support than any Glock barrel. Look at the case head and primer flash hole for cripe’s sake. The case head is expanded all the way out to hard contact with, and mashed against, the inside of the slide. A weakened case doesn’t extrude like soft butter and squirt out the back of the chamber either. Not unless it’s made of modeling clay.

      “Often reloaded, hence weakened” brass is work hardened too, and even less likely to extrude like that unless you’ve annealed the case heads, which would be dumb. Good golly, Man, take a couple of minutes to look at the evidence. We spent hours putting it all together.

      Only a way, way over pressure event would create those results.

      Do I know for 100% certain, beyond all shadow of doubt that it was a double charge? No. That’s why I used the word “probably”. But I’d certainly bet that it was. Any other possibility gets us into the land of the bizarre, the freakish, the highly, highly unlikely. Maybe the case was actually made of molding clay, which looked and felt just like brass, but it held well enough to put up a number of over 1,500 fps on the chrono.

      You could suggest that the previous round was a squib which left a bullet in the bore, but it for 100% sure and for certain wasn’t a squib. Maybe an alien spaceship approximately the size of a bullet flew into the bore right before he took the fateful shot. I’ll give you that possibility. But a double charge is somewhat more likely.

      The shooter brought up the old “an under charge can actually detonated and blow your gun” meme, but I dismiss such my the as never having been scientifically verified, and anyway old black powder cases now used with smokeless, such as the 38 Special and 45 Colt would be blowing up right and left if that were the big danger. The condition of the case says for 100% sure that it was a massively over-pressure event. The previous round went of perfectly, cycled the action and have a consistent chronograph reading, so for there was no bore obstruction unless that little alien spaceship flew into it. The gun was in full battery, and the case was not faulty. You tell us then, Mr. Smarty Pants, what happened. Maybe someone slipped some C4 in the case.

      He’s a new reloader, using a single stage press. Again; he said he carefully measured each charge, which pretty well means he wasn’t using a progressive. You can bet your sweet bippy he’s going to visually inspect each case from now on, before the bullet goes in.

  4. Same with motercylists, those who have gone down,,,,,and those who havn’t (or will)….

  5. Part of the reason good gloves are standard PPE for me when shooting…

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