Detonation, another myth?

trebor2880

trebor2880

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Been Googling and looking on other sites about the validity of detonation occurring with using a too light of load with reloading.
Some say it's never been proven, others say it's likely mistaken for a double charge. No concrete proof. What do you think?
My manual states the starting load of a 180gr. bullet is 6.0 gr.(Power Pistol) in the 40S&W with a 1.115 OAL.
I'm down to a comfortable and reliable 4.5 gr. with an OAL of 1.125. Just 75% of what is recommended for the powder.
I've loaded 45ACP loads down to where they are just powerful enough to cycle the slide, with no ill effects.
Detonation. Fact or just another old wives tales of the shooting world. Or am I pushing my luck?
 
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I'm not sure, but I do know that some powders are rated for "light" loads like H4895- Hornady says it can be used in very light loads because it ignites safely regardless of case "fill".

I think it is possible to have too light a load for some powders. The mode of failure looks something like primer ignites but doesn't start the powder burn. The primer pushes the bullet into the rifling where it gets stuck and then the powder ignites causing an over-pressure. I know some rifle shooters load jammed but from what I can gather not all powders burn reliably when overly light loads are used.

I can't comment on your specific situation... pistol powders do have very high burn rates so maybe it isn't an issue?
 
I think the detonation is more of an issue with black powder cartridges than smokeless powder. I don't have any experience with black powder cartridges, but remember reading something about cases not being full enough being dangerous.
Kristian
 
I've come across a few such discussions and the result always seems to be that detonation with smokeless powders is pretty much a myth. The only issue seems to be if you go too light the charge may not burn well or it may even not ignite at all.

Some powders work well when used at small amounts and some do not. And with semi autos you're more or less self limited anyway by the need for enough pressure and recoil that the action cycles. Now if you want to see and "not hear" some really light loads you need to hang around some cowboy action shooters. I don't cotton to those super light mouse fart loads but some do. And one guy right now is running such light amounts of Titegroup that the sounds of his shots are highly variable. A definite sign of going TOO low. The issue being that the burn is now inconsistent and he's on the ragged edge of the powder not burning correctly at all and getting squib loads that stick the bullet in the barrel. And then if he doesn't notice it the next one can cause big issues...

With black powder ANY AIR GAP AT ALL is going to produce higher pressures than normal. All black powder loads are supposed to have the bullet seated firmly on the powder and no air gap. If folks want to play with lower powder levels with black powder they need to use a filler like oat bran or cream of wheat cereal as a filler so the powder charge is still firmly compressed.
 
For real light loads I use "Trail Boss" in the 40S&W and 45ACP. Can't get enough powder in 9mm cases to cycle the slide, with out compressing the powder.
 
Read about it years ago and I doubt it is a myth. Usually it involves using a very light charge of very slow burning powder in a chamber with a gradual throat taper ( lead). While it is not a perfectly repeatable load I did read of an experiment many years back in Sweden or Norway (?). I think it involved a transducer on a 6.5x55 using the LIGHT LOAD of a SLOW powder and the load showed several high spikes in pressure. The theory ( unproved ) is that the primer drives the bullet into the throat, where it momentarily stops, before the powder is ignited. Upon ignition the powder now burns but pressure spikes because of the bullet being wedged in the throat. As a millwright I've seen pneumatic cylinders with a worn piston SLIGHTLY detained in its movement but pressure building behind it, suddenly release with with a BANG. Other equipment will do the same, it's called STICK/SLIP. The other phrase for this (in firearms) is called SEE, Secondary-Explosion-Effect. Can't be proved, can't be repeated on demand but I personally wouldn't want to put my beautiful face behind a bolt holding a light charge of slow powder just to save a few pennies on powder. Lots of other options are available.
 
This detonation, or SEE, is NOT a myth. It occurs with reduced charges of slow-burning powder.
Certain powders used to have a warning acompanying them regarding using too low a charge weight.

As has been mentioned, the phenomenon cannot be duplicated at will, but occurs without warning.
I had a personal experience many years ago with old W785 in a 308 Norma Magnum. It did not destroy
my rifle, but the signs of extreme pressure were very evident. After beating the bolt open with a 2x4,
the case came out and the primer fell right out of the case. The head of the case was heavily marked,
and it measured .536" across the belt. I was shooting a charge that gave me about 2400 fps with a 180,
and had shot quite a number before the kaboom happened. All the others acted absolutely normally. I
changed over to IMR 3031 for my reduced loads, and never had a prblem again. Dave.
 
Eagleeye, I had a similar situation with a 6mm Remington chambered Mod 700.

I won't go into much detail other than I was using Norma MRP over standard Large Rifle Primers in unfired bass with 100 grn spire points. The rifle was from the Remington Custom Shop with a 25 in, 1-8 twist #3 contour barrel.

I don't remember the charge weight of MRP but I do remember it was light as I was forming the cases to the tight chamber.

There was one heck of a kick and a huge muzzle flash and I couldn't open the bolt by hand either. I didn't want to pound on a new rifle so I sent it back to the Custom Shop. I told them what had gone on and that whatever occurred was likely my fault. They pulled the barrel and knocked out the brass. They sent it all back to me and explained about slow powders in medium or larger cases under relatively heavy bullets. They suggested a faster powder and lighter bullets for fire forming as well as a load slightly over minimum suggested spec.

The problem occurs when there is a large air space in the cartridge and the bullet is seated close to the leade. The powder should burn at a controlled speed which is in part regulated by the space in the cartridge. When there is a lot of air space the powder burns much faster to the point of being a detonation. It doesn't happen often but from what I gather, Norma MRP which may or may not have been W785 has been involved in more than its fair share of these incidents.

At the time, I was young and inexperienced, I felt the small charge of slow powder would actually increase the safety margins in such a tight chamber. Just for clarification, the chamber on this rifle was cut to absolute minimum specs with a neck that would be considered a custom neck. I had to get Huntington's make up a special set of dies for this chamber. I had difficulty chambering even new unfired brass. It was an extremely accurate rifle once I went through the learning curve. I put about 1200 rounds through it before selling it to the late Al Forslund who shot it for a few years before it started to lose accuracy. He set the barrel back 4 threads to clean up the leade and used it for more years. I don't know where that rifle is now.
 
I think it's rare in small pistol cases, never heard of that happening in a 9/40/45.
H110 is a powder that specifically states don't go below min or possible detonation can occure, but it's more of a magnum pistol, small rifle powder.
Where I have seen most KB's is lead plinkers using pistol powder in bigger rifle cases. Hard to nail it down after the fact of course that it wasn't a double charge. I sold a K31 to a fellow that blew it to bits using those sort of plinking loads.

I shoot lots of old guns, a few 100+ years young, but always with light rifle power loads and jacketed bullets. I won't go below 80% case capacity with any powder.
 
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Some powders have warnings. There is a reason.

There is an "appropriate" powder for each task. If you don't have that powder, one can usually find one that is good enough. But what does not work is using a slow powder intended for max velocity ammo and trying to download it for plinkers. For plinkers, use a faster powder.

OP, Power Pistol is an excellent high velocity powder, and it can be down loaded a bit. Don't go below the book Start load. A more flexible powder is Universal or Unique.
 
I have personally inspected two revolvers that had the top of the cylinder as well as the top strap blown off. I highly doubt that even a double charge could have that effect.

Double based powders have a nitroglycerin content. I believe the theory is that a very light load causes incomplete ignition which allows the powder to smoulder which vaporizes the nitroglycerin. The nitro vapour then detonates and destroys the gun. Again this is only theory as nobody seems to be able to reproduce the effect.

I have gone as low as 30% load volume in subsonics for large rifle cases. There are a couple of techniques used to ensure proper powder ignition.
 
hogie said:
http://www.canadiangunnutz.com/forum/showthread.php/912891-Lucky-day

Here's a link to what happened to me. Some good info in there about secondary explosion.
Click to expand...

I believe the end conclusion of your incident was incorrect. I highly doubt a ca 35gr load that is book published could cause SEE.

You actually noted the cause of the ruptured case in your thread but nobody picked up on it. That rifle had a massive excess headspace compared to the case. That resulted in a ruptured case head which allowed 60,000+ psi of gas pressure to enter the receiver and smash things up in the process. I've seen it personally with similar results.

Your pic of the split case head just screamed excess headspace to me and your chamber measurements confirmed that.
 
Suputin said:
I believe the end conclusion of your incident was incorrect. I highly doubt a ca 35gr load that is book published could cause SEE.

You actually noted the cause of the ruptured case in your thread but nobody picked up on it. That rifle had a massive excess headspace compared to the case. That resulted in a ruptured case head which allowed 60,000+ psi of gas pressure to enter the receiver and smash things up in the process. I've seen it personally with similar results.

Your pic of the split case head just screamed excess headspace to me and your chamber measurements confirmed that.
Click to expand...

17 thou is nothing, not for new brass anyway, should be able to handle that easy....and that starting load would not have been 60,000psi.
Something else going on there.
Pretty much every Nork M14 out there is running 15-20+ thou over 308 specs and there are probably millions of rounds through those combined. Steel cased don't seem to handle it so well however.
The case head looks very thin in the pics, and I don't see any signs of brass flow anywhere, just the case coming apart.
 
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I had found an interesting article on SEE after that happened. They were having it happen with published data and low charge . Problem is duplicating it. I wish the article was still on the net.

One of those things that not easy to find info on.
 
Hitzy said:
I think it's rare in small pistol cases, never heard of that happening in a 9/40/45.
H110 is a powder that specifically states don't go below min or possible detonation can occure, but it's more of a magnum pistol, small rifle powder.
Where I have seen most KB's is lead plinkers using pistol powder in bigger rifle cases. Hard to nail it down after the fact of course that it wasn't a double charge. I sold a K31 to a fellow that blew it to bits using those sort of plinking loads.

I shoot lots of old guns, a few 100+ years young, but always with light rifle power loads and jacketed bullets. I won't go below 80% case capacity with any powder.
Click to expand...


Hitzy, can you elaborate on the K31 light load that caused this?

I run light loads in mine, and don't want to ruin the classic rifle.

I run 39grn of 4064 and similar powders. It came from the Swiss rifle forum and works great in mine, very accurate and nice to shoot, but I would change it if need be.
 
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