Under Charge and Overpressure

[bigedp51]

When did a 44 mag get to be a large case. I think you have missed the point he was asking.
Good Shooting Larry

Hold a 9mm and a .44 Magnum case in your hand, which is LARGER?

And reduced loads in large rifle cases with jacketed and lead bullets are loaded to below 40% of case capacity all the time. Detonation with slow burning powder happens above 40% of case capacity in larger cases as I pointed out with the .32 Special and 8mm Mauser example with the same weight bullet and powder charge.

The OP said NOTHING about large cases or 40%, he asked the following:

Re: Under Charge and Overpressure

Can someone point me in a good direction to understand why excess pressure happens when a load isn't fully charged. I have read some explanations but still don't understand. This isn't a question about wrong powders but about a less than full charge resulting in dangerous pressure. Thanks

Now "WHO" is missing the point of the OP question and apparently never shot reduced loads?

P.S. Its OK to do a slow burn after reading this, but please do not detonate and try and reach critical mass at 40%, you will just end up a dirty bomb and cause the forum members to loose all their hair.

 

[BoydAllen]

Absolutely none of this is about pistol loads or powders. I hope that you are kidding with those references. One of the classic cases would be something like a .270 Winchester that some fellow wanted to load down for with the same 4831 that he had been using for his normal loads. By going well below the minimum manual load with slow powders in larger rifle cases, disastrous things have happened. If you think that Ackley only was familiar with and shot his own case designs, you have not read his books.

 

[bigedp51]

Absolutely none of this is about pistol loads or powders.

Mr. BoydAllen

I'm very sorry but you are in error, in my 44 magnum posting I said I was shooting 7 grains of Titegroup a fast burning pistol powder.

BUT the same .44 magnum case and bullet can be loaded with 28 grains of the slow burning Winchester 296 powder.



Winchester had the same warning about 785 rifle powder and later took it off the market because of detonation problems with loading densities below 89%.

Winchester had even placed warning about load densities with 748 and 760 in their reloading pamphlet. It is the slower burning powders and low loading densities that were causing the detonation problems. And it didn't matter if it was a rifle or hand gun cartridge.

The "Big Bang" theory covers the entire universe and NOT just rifles.

 

[BoydAllen]

You did not give any information about what caused the damage in your pictures. Were they attributed to too light of a load?

 

[savagedasher]

785 is slower burning then 4831 and it not made for any pistol. The reason they took 785 and452 off the market it was too close to the other powders the made. Good Shooting Larry

 

[bigedp51]

You did not give any information about what caused the damage in your pictures. Were they attributed to too light of a load?

From what I remember I think it was a light 180 grain bullet bullet used with the same 23-24 grain charge of 296 he used with his 240 grain bullets and it detonated. I have quite a few KB photos of rifles and pistols and use them to wake people up.

 

[bigedp51]

785 is slower burning then 4831 and it not made for any pistol. The reason they took 785 and452 off the market it was too close to the other powders the made. Good Shooting Larry

First you make up the 40% rule that changed to the 30% rule and now you say 785 powder was taken off the market because Winchester had two similar powders. Brilliant deduction...............

How about Winchester replacing their biggest kaboom powder with a newer safer powder that didn't detonate as easily as 785 did.

 

[bigedp51]

"SEE is an unexplained pressure excursion which has often blown up guns. It is associated with markedly reduced loads of very slow powders.

Contrary to the ubiquitous old wives tale, detonation is NOT a consideration with fast powders such as Bullseye, no matter how light the charge is or how spacious the case.

The phenomena of Secondary Explosion Effect (SEE) is known to occur only with the slow powders at very low loading densities. Precious little is known about the mechanics of the phenomenon and it is not even known if the expression, Secondary Explosion Effect, is accurate. SEE, despite best efforts of the leading powder companies, cannot be reproduced in the lab, at least in the literature that I have been able to find. Some of the powder companies now are putting notations in their manuals not to reduce CERTAIN loads below 80% loading density. One should note that such notations are for a very limited number of powders and cartridges, such as W-W 296 in the .44 Magnum. Actual documented SEE cases were at densities much less than 80% and with slow powders."

Danger! Light loads in big cases can blow up.

http://www.reloadammo.com/liteload.htm

 

[BoydAllen]

We live and learn. Thanks for the additional information. I learned something today.

There are so many powders and bullets, that I can usually find one that is in a manual that fits my needs.

This whole thing reminds me of a blowup that happened to an elderly shooter a number of years back. He was shooting 173 gr. gas check bullets in a Savage 110 .30-06 with a common load (17 gr. if I remember correctly) of 4227. It was always the thought that it was a double charge, but some time later someone said that they had run the numbers and it shouldn't have done the damage that it did, even with the double charge. I have most of the parts in a box. The top of the receiver ring split off. The barrel was launched, the stock split, and the bolt bent upward from the front of the front receiver ring at about a 30 degree angle. The scope suffered the same fate, and the gas block behind the bolt head disappeared. The barrel was swelled at the back so that its nut could not be removed. Luckily, because he had his left hand on the rear sand bag, he was not seriously injured. Perhaps it wasn't a double charge, but I do know that the load is listed in a cast bullet manual.

 

[Curmudgeon]

I would like to thank all for the response to my question. It was in no way meant to be a trick question. My reference to full case loads comes from my practice of finding appropriate powder and bullet for accuracy with as close to a full case without crunching. There was an incident, fortunately without injury, that resulted in a destroyed 300 WSM. The shooter made every effort to practice safe reloading. At first the conversation tended to wrong powder but the event took place in the middle of a string. Someone then asked about a poorly charged case so the conversation started to surround the question " what happens to pressure when a case is less than full". Since this happened with a slower burning powder in a larger case the responses seem pertinent. Thanks again.

 

[bigedp51]

Mr. BoydAllen

In the world of fast action pistol shooting they are using heavy bullets and fast powders. This gives competitive shooters less or softer recoil and the ability to recover faster between shots. I only bring this up because of the incorrect comments made here about light charges of fast burning powder and detonation.

Below are some of the loads I'm using in my .40 Glock.

Make Right With a “.40 Lite”
http://www.handgunsmag.com/2010/09/24/ammunition_40lite_091806/

 

[savagedasher]

Some how you got off the subject pistols was never involved you were the one who brought it up
Good Shooting Larry

 

[bigedp51]

Some how you got off the subject pistols was never involved you were the one who brought it up
Good Shooting Larry

Under Charge and Overpressure
Can someone point me in a good direction to understand why excess pressure happens when a load isn't fully charged. I have read some explanations but still don't understand. This isn't a question about wrong powders but about a less than full charge resulting in dangerous pressure. Thanks

Loading density applies to all cartridges pistol or rifle alike, now take a deep breath and calm down.................and STOP sending PMs telling me how great you are.
Your breaking my 30% to 40% obnoxious rule......... :

Now excuse me, I have some steaks to marinate in nitroglycerin and detonate tomorrow for supper.

 

[BoydAllen]

I went back to the start of this thread and he did not specify, but I think that most of us assumed that he was referring to rifle loads, since this is the primary focus of this site. Nevertheless, if there is something to be learned about guns blowing up, I am always open to new information. As a former range board member and president, I have spent more time than many dealing with safety concerns, and frankly, dealing with the resistance to safety rules has made me a bit cynical about human nature. I guess that the main thrust of all of this is to stick to the manual as far as light loads go, especially with slow powders.

 

[bigedp51]

I went back to the start of this thread and he did not specify, but I think that most of us assumed that he was referring to rifle loads, since this is the primary focus of this site. Nevertheless, if there is something to be learned about guns blowing up, I am always open to new information. As a former range board member and president, I have spent more time than many dealing with safety concerns, and frankly, dealing with the resistance to safety rules has made me a bit cynical about human nature. I guess that the main thrust of all of this is to stick to the manual as far as light loads go, especially with slow powders.

It happens when a large case is used with a fast burning powder. You get secondary ignition. When you use 20 gr of powder in a case that holds 75g you must us a filler. That keeps the powder charge next to the primer not at the bullet end. Good Shooting Larry

savagedasher, that only applies when your making Quaker Puffed Rice and only using 2.7 grains of Bullseye. :

 

[7x57 Shooter]

I believe a reduced load would not have the correct pressure to launch the bullet at full speed, the bullet then becomes a barrel obstruction that raises pressure. This causes the gas to go somewhere other than down the tube where it's supposed to go.
I do not use reduced loads or fillers because I have heard that fillers can obstruct the barrel as well.
There is quite a bit of data in the manuals that show the proper powder and charge, I don't bother, if I want to shoot at a slower velocity, I will buy a smaller gun.

 

[BoydAllen]

There are reduced loads for some rifle calibers in reloading manuals. Hornady used to have them for some calibers. Typically they use powders that are faster than are usual for the caliber. In the past, I have shot these loads with good results. I think that the main issue here is with people improvising with the wrong components. If you stick to the books, you should be in good shape.

 

[Curmudgeon]

Not to get off topic this question is not about improvising loads. This was a tried load that was dropped into a case. A visual inspection before placing bullet should reveal a case with a less than needed amount of powder. This might have been the case here, missing a short load. Hence the question " does excess pressure develop"? Thanks again

 

[bigedp51]

German scientist explaining Dasfirespittenlounenboomer or Detonation.

Detonation misnamed as "seconday Explosion"
http://lutz-moeller-jagd.de/English/Detonation.htm

"If You only partly fill a long Cartridge with heavy and dense Powder grains, that is slow burning double based Powders, only partly the following will occur, if Powder happens to be on the lower Part of the Case. The Primer flash reaches the Powder from behind. The Powder partly ignites from the bottom and generates Pressure. Before is no Pressure Yet. When enough heavy and dense Powder grains jam against the Case shoulder or the Bullet bottom, the mechanical Push may detonate them. If only one detonates and others are near by a Chain reaction will follow and the hole Cartrigde will explode and the Rifle will follow suite. BANG!

Now we understood, how a Detonation works, Means to control it are obvious. Avoid free Acceleration lengths!

Rule 1: Always fill any Cartridge full. That is the Volume inside wit the Bullet seated must contain less the 5% empty space. I do not mean the Space between the Powder grains, but she poured Volume. If You consider the Case Volume alone, like QuickLoad does, anything less than 90% is bad. As a practical Rule fill any Case a t least up to the Shoulder, never less.

Rule 2. A stuffed Case, that is with a compressed Load, is the safest. First no free Acceleration length exits and second whn You shake ita nd it rattles You know the load is incomplete and and dangerous, even when You have no Scale at Hand and not made the Ammunition by Yourself."

 

[bigedp51]

I believe a reduced load would not have the correct pressure to launch the bullet at full speed, the bullet then becomes a barrel obstruction that raises pressure. This causes the gas to go somewhere other than down the tube where it's supposed to go.

Hodgdon's has a very good webpage on reduced loads, if you notice it is the single base powder H4895. Also some of these loads are in the 50% range of loading density and the rifle are not blowing up.

As an example a youth model in .308 Winchester would benefit young shooters starting out with reduced loads. And factory Managed-Recoil ammunition is only loaded to 2600 fps with a 125 grain bullet.

Hodgdon® H4895® REDUCED RIFLE LOADS for
Youth Hunting, Informal Target and Plinking
http://www.hodgdon.com/PDF/H4895%20Reduced%20Rifle%20Loads.pdf

308 WINCHESTER, 125 GR. NOS BT, 2592 fps 31,600 CUP