Explosions?

[MCgunner]

I've read articles in the past cautioning loading squib loads with fast burning powders in large cases due to a phenomenon where the powder burn rate accelerates or something, and over-pressures by a bunch. Now, I've never heard of this happening and load my own squibs in .38 special, though not a particularly cavernous case. I've often wondered about this. I wouldn't want such a squib in a rifle caliber because of the fact that the powder ignition might be iffy depending on the proximity of the powder to the primer. Not that it wouldn't go off, just that there'd be a variance in ignition timing.

What's the thoughts? Anyone ever hear of a gun blowing due to squib loads with fast powders? Anyone read about this stuff, have any opinions?????

 

[Father Knows Best]

I've heard of it. There is a lot of controversy about what is really happening. We all know that small amounts of powder in large cases can cause erratic ignition and burn patterns. I've seen articles on the impact of powder positioning on velocity, with tests done by pointing a revolver skyward first to allow the powder to settle back against the primer for some shots, and pointing it downward before firing to get the powder up against the bullet. The upshot (pardon the pun) of it all is that you don't get good accuracy when the powder can move around a lot, because you introduce too much variability.

There are also reports of light loads detonating instead of burning, and causing guns to blow up in the process. I read an article online a year or so ago in which the author claimed to have blown up a T/C Contender with a very light load. As you probably know, smokeless (nitro) powders are classified as "propellants" not explosives. They are supposed to burn, not detonate (explode). Some people believe that under the right conditions, a small amount of a nitro propellant in a large case can actually detonate, much like a dust explosion in a grain elevator.

As I understand it, however, there is a lot skepticism about these claims. No one has been able to make it happen under controlled conditions (in other words, "on purpose"). The skeptics believe that most of the reported incidents are actually the result of double charges, which of course can easily happen with small quantities of a fast powder in a very large case. The skeptics point out that the people reporting these incidents have no way to prove that the loads weren't double charged, and that they have a vested interest in claiming they weren't, i.e., they'd rather blame a freak phenomenon than admit they screwed up loading the round.

I don't know what to believe. I'm a skeptic by nature, though, so I tend to think that until someone can replicate such a detonation under controlled conditions, it's more likely myth than fact. Still, I am a careful reloader. I load some big ole black powder era cases (.45-70, for instance), and sometimes use smokeyless propellants. I am very careful to inspect each case, and stick to minimum safe loads listed in published reloading manuals.

 

[Steve C]

The powder detonating has been a theory of why some pistols where taken apart when they where shooting light loads. Usually these loads where with Bullseye powder and wad cutter bullets. Years ago there was an article in the American Rifleman, I believe, where the author and the people at Hercules ballistic laboratory tried to reproduce the conditions. After 1000's of rounds of light loads they could never reproduce a detonation. They where able to get pressures that would cause catastrophic failure in even a .357 mag by using a triple charge. Their conclusion was these catastrophic failures where most likely do to accidental overcharge rather than any kind of powder detonation or explosion.

 

[Grump]

I first heard about it back in the days of 2.7 grains of bullseye under a 147-gr full wadcutter deep-seated in a .38 Special, the classic Bullseye pistol load. Don't hear that much about it now.

According to one report I read (all cautions apply here), H.P. White labs did some testing and found that modern Colt and S&W .38 Special revolvers, like the ones reportedly with cylinders blown open by this load "detonating", would easily hold up to double and even triple charges of this powder under that bullet.

I believe the only theory to hold water, to be remotely "proveable", is that light loads of pistol powder in blackpowder rifle cases *can* but don't always put a ring in the chamber...especially if a filler is used. It also supposedly happens only with older, milder steel barrels...FWIW.

 

[ReloaderFred]

I've seen two .38's blown up using Bullseye. One was a member of our team who was shooting next to me in a match. He had loaded his ammunition the night before and was in a hurry. We had one of the old C-H inline progressives and the transfer bar would sometimes skip over the cases and not move them to the next station. If you weren't paying attention, it would double charge.

When his Model 19 grenaded, pieces went everywhere, including the Bomar Rib, which ended up bent like a horseshoe. He admitted that he had probably double or triple charged the case, because he was tired when he was loading and was in a big hurry.

H. P. White labs was never able to replicate the detonation theory in all their testing. Neither was Hercules, when Bullseye was being used by the ton during the heydays of PPC shooting. I've shot close to 100,000 rounds of 2.7 grains of Bullseye under 148 grain hollowbase wadcutters and gotten nothing but accurate rounds, with no hint of accuracy or ignition problems.

I believe that the two guns I saw blown up were the result of double or triple charges of Bullseye, which will produce more pressure than a cylinder can withstand.

The bottom line is to use caution whenever reloading and pay close attention to what you're doing. Eliminate distractions and constantly check to see that everything is as it should be. I still load 2.7 grains of bullseye and have all the confidence in the world in it.

Hope this helps.

Fred

 

[mete]

There definitely can be explosions or 'detonations' with reduced loads of very slow powders and this has been reproduced in the lab. For fast powders the only problem , again reproduced in the lab, it that it's easy to double or even triple charge or load two bullets , this easily gives you pressures of 70,000 psi which will immediately take apart your revolver !!!

 

[Father Knows Best]

There definitely can be explosions or 'detonations' with reduced loads of very slow powders and this has been reproduced in the lab.

Citation, please.

 

[Sport45]

There definitely can be explosions or 'detonations' with reduced loads of very slow powders and this has been reproduced in the lab. For fast powders the only problem , again reproduced in the lab, it that it's easy to double or even triple charge or load two bullets , this easily gives you pressures of 70,000 psi which will immediately take apart your revolver !!!

I believe this is what Lee says in his book. He has a section on reduced loads and advises against reducing the slower rifle powders. According to him fast pistol and shotgun powders can be reduced without fear of anything but sticking a bullet in the barrel. That's the way I read it, in any case.

I've used 3 to 5 grain charges of Titegroup under heavy cast bullets in .375win and 7.7jap with good success. Talk about a little dab of powder that's lost in a big case. Without exception (even though a double charge of this would still be "safe" in these cartridges) I would immediately seat the bullet after dumping the measured (often volumetrically) charge.

I got a lot of unburnt powder when I tried reducing H4895 using Lee's formula. After that, I just went to Titegroup for the popcorn loads. My sons are much bigger now, and I don't do the "gallery" loads any more. Maybe again when I have grandchildren.....

 

[CodeSlinger]

From Lee's Modern Reloading, 2nd Edition, pp.52-53:

It's obvious that too much powder will cause too much pressure and be dangerous. What is not so obvious, too little powder, of a very slow burning variety, can sometimes cause too much pressure. Do not become obsessed with worry about this rare phenomenon. The conditions are quite limited.

These are the conditions and they all must be present:

1.) It only happens with very slow burning powders--the kind normally used in small caliber large capacity cases.

2.) The reduced charge must be 25% to 35% under normal.

3.) Something special must happen about which no one knows the details for certain.

Conjecture includes:

a) Wave pulses.

b) The bullet starts then stops then builds excessive pressure to restart the bullet.

c) The powder wedges against the shoulder and compresses to form a stopper.

d) A small charge evenly distributed horizontally acts as a shaped charge and direct pressure to a small area on the top of the chamber.

Laboratories have been unsuccessful in replicating the event; so scientific study is not practical.

Mention of the phenomenon is to encourage you to avoid greatly reduced charges of very slow burning powders. If you want a light load, use a medium burning powder. For an ultra light load, use a very quick powder.

Emphasis mine. This edition was copyrighted 2003, I can not say whether anyone has been more successful since then.

 

[MCgunner]

Hmm, well, I've loaded and fired tens of thousands of 2.6 gr B'eye behind a Lee 148 grain WC and never had a problem except once when I got a round that had no powder and the bullet stuck in the very end of my M10. That's when I learned I should check all my cases/powder levels after charging them, compare them with the others in the tray. That's my check against overcharges or non-charges. But, I use the powder through expander die and a Lee disk loader. On my progressive, all I've done is 9mm with charges of unique that make it impossible to have a double charge in that small a case. However, this is a concern if I buy .38 or .45 dies (I intend to) for the Dillon. I will have to be especially vigilant loading those WC loads or my B'eye .45 loads. Lesson for the day, I reckon. Thanks for the comments! I don't intend to ever load when I'm bone tired anymore, either, LOL!

 

[Waffen]

It's called Pressure Excursion Phenominon. As previous posters have stated it's pretty much only when you have a small charge inside a large volume case and all the powder is ignited instantly causing a massive rise in pressure. I have never seen or had it happen, however if you do a search on Accurate Reloading or on Long Range Hunting there were a few good threads there.

 

[JMusic]

My opinion is to follow reloading manuals religously. Most give squib loads for high power rifles and pistols. Remeber don't try to remove a stuck jacketed bullet, you will only ruin your barrel. Don't be a pioneer when reloading. They say its easy to find a pioneer, the're the ones laying out in the field with arrows in their backs.
Jim