February
S M T W T F S
1 2 3 4 5 6
7 8 9 10 11 12 13
14 15 16 17 18 19 20
21 22 23 24 25 26 27
28
Who's Online Now
1 members (skeettx), 141 guests, and 6 robots.
Key: Admin, Global Mod, Mod
Forum Statistics
Forums10
Topics35,305
Posts497,621
Members13,980
Most Online462
Aug 5th, 2016
Previous Thread
Next Thread
Print Thread
Page 5 of 5 1 2 3 4 5
Joined: Dec 2006
Posts: 16
Boxlock
Offline
Boxlock

Joined: Dec 2006
Posts: 16
Originally Posted By: craigd
I can appreciate that you are distinguishing a shock wave from pressure, it still does appear that the phenomenon tends to happen in large cases loaded to relatively low pressures.


I would change this to read, it still does appear that the phenomenon tends to happen in large cases loaded to relatively low pressures when less than ideal propellants and questionable loading practices are used.

...and before jumping all over me, this is not aimed at anyone, I include myself in that category. I don't think you'll find a powder company or loading manual publisher that would consider stuffing a varying amount of Dacron, foam, cream of wheat, or dryer lint in a cartridge as a recognized loading practice. We don't do it because we want to, we do it because we need to if we want to duplicate original black powder ballistics in many cartridges that werenít designed for smokeless powder. The proper powder to use to achieve factory ballistics would be black powder. There's a reason you see powders with names like 50BMG and CFE223. They were designed to have the ideal density and burn rate to work in those cartridges. We don't have a smokeless propellant that mimics the density and burn rate of black powder in all situations so we have to make do with what we have and with that comes risk.

Originally Posted By: craigd
The question would be, why doesn't this condition happen in what are commonly known to be high pressure cartridges. Automatic and semi automatic actions would seem to be dangerously vulnerable to feed and extraction problems, but it doesn't seem to happen?


If we look at modern rounds like the 308 and 223/5.56 they were designed to work with smokeless powder. Their target velocity is achieved with powders that fill the case and work at target pressures. If we were to neck down a 300 Ultra Mag to 22 and try to mimic 223 ballistics we'd run into the same problem. There just isn't a powder that will allow us to easily achieve that without risk.


Originally Posted By: craigd
As an aside, while the dicussion is about ringed chambers, I would think it also relates to some blowups.


Kinda, sorta, maybe???
Again I will do my best to oversimplify this. Please don't jump on me if things are not totally accurate. Excepting obstructions, blowups are generally going to be a result of using too much powder. This will be more common when fast powders are used as less is needed to reach high pressures. In some cartridges two or even three times the max charge can be placed into the case. This is less of an issue with slower powders as more is needed to reach the same pressure and you often run out of space before you can reach a pressure high enough to blow up an action. That said this will apply more to the individual that uses Red Dot in a 30-06 rather than the individual that goes two grains over max with a charge of Varget. The latter is certainly bad but is less likely to result in a blowup.
Smokeless powders are engineered. Thereís single base and double base. Thereís flake, ball and extruded. Some grains have holes in them others donít. Some grains are bigger than others. All this is done to modify the density and the burn rate to allow it to perform optimally in a cartridge (or several cartridges). This engineering is almost always done to slow the burn rate. Fast is easier to achieve.
Why do we care about burn rate? As I mentioned before itís not just the pressure we care about itís how fast the pressure is created as well.
If I place a car in neutral on flat ground and run into it at 10 fps with my 200 pound body weight I will exert 311 pounds of force on the car. If I assume my arm weight 10 pounds and I slap the car with it at 50 fps I will exert 389 pounds of force on the car. Which one will move the car further? Which one will hurt more? I hope most will agree (otherwise my example sucks) that the first despite being less energy will move the car further and hurt less. Again itís not just the total energy itís how and when the energy is released. Another example is in mining. Letís assume we are quarrying granite and long bore holes are drilled in the rock. If those holes are filled with a slow explosive the granite will separate in large chunks. If a fast explosive is used you will get stone dust. The total pressures can be made to be the same but the results will be different. This hopefully helps you to understand why we choose one powder over another.
If we use a very fast powder in a cartridge it is possible to raise the pressure so fast that the action fails before the bullet can be expelled. Thatís the reason we canít use high explosives in guns. In a perfect world the propellant would start burning slowly until the bullet began to move and then rise to max operating pressure and stay there until the bullet just leaves the barrel where it would be totally consumed. Unfortunately they donít work this way. They usually work just the opposite and reach peak pressure quite rapidly and then drop off as the powder burns and as the internal volume increases (due to more barrel length being available as the bullet moves forward). The powder manufactures try to make a powder that will fill the case and slowly and over time push the bullet forward so the chamber pressure stays in the target range without going over. So why donít we just use slow powders for everything? A byproduct of modifying/slowing the burn rate is that those powders require higher pressures to fully combust. If the case volume is too big and the projectile too light the powder will not burn completely (if at all) and you often get a bullet stuck in your barrel. In many pistol cartridges the pressures needed to ensure a good burn with slower propellants are higher than the pistol can withstand so you need to go to a faster powder to get it to burn at the lower pressures. This is why there are so many different powders and why not all work in every situation (cartridge). This is why high volume cases (usually originally designed for black powder) require faster powders and have more room in the case than needed. This room allows for the potential of double charging (with a powder thatís less forgiving) and these fast powders and air space can also lead to the chamber ringing. I guess they are related in that way but the reasons they happen are different and the mechanisms that create them are different.

Joined: Feb 2009
Posts: 6,997
Likes: 6
Sidelock
**
Offline
Sidelock
**

Joined: Feb 2009
Posts: 6,997
Likes: 6
Originally Posted By: dearmer
....Which one will hurt more? I hope most will agree (otherwise my example sucks) that the first despite being less energy will move the car further and hurt less....

Ah, but there in lies the rub, on the arm that is. Does the arm move the car less because some of the energy was expended to create the hurt, not movement?

Just kidding. Hey dearmer, thanks for taking so much of your time to lay your explanation.

Joined: Jul 2012
Posts: 3,632
Likes: 4
Sidelock
**
Offline
Sidelock
**

Joined: Jul 2012
Posts: 3,632
Likes: 4
dearmer,
Just for information, slow powders in rifles can cause blowups. A famous example is the case of 270 Win. loaded with less than the recommended amount of 4831. This is another one I have never seen but has been reported enough that it must have happened. Enough cautions have been given about this that instructions for loading 5.6X61 vom Hofe S.e. make particular mention of it. Also One of the Engineer BNs I was in ran a quarry for training. Military Dynamite was used in blasting( fairly slow) with good success, but when the ran out and used some C4 (much faster)they didn't get dust, the got chunks as large as house trailers, whish had to be blasted again to get them small enough to fit into the crusher. The Dynamite would "heave" it, but the C4 would "shatter" it along fault lines. I don't know if this affects your examples or not.
Mike

Joined: Dec 2006
Posts: 16
Boxlock
Offline
Boxlock

Joined: Dec 2006
Posts: 16
Originally Posted By: Der Ami
dearmer,
Just for information, slow powders in rifles can cause blowups. A famous example is the case of 270 Win. loaded with less than the recommended amount of 4831. This is another one I have never seen but has been reported enough that it must have happened. Enough cautions have been given about this that instructions for loading 5.6X61 vom Hofe S.e. make particular mention of it. Also One of the Engineer BNs I was in ran a quarry for training. Military Dynamite was used in blasting( fairly slow) with good success, but when the ran out and used some C4 (much faster)they didn't get dust, the got chunks as large as house trailers, whish had to be blasted again to get them small enough to fit into the crusher. The Dynamite would "heave" it, but the C4 would "shatter" it along fault lines. I don't know if this affects your examples or not.
Mike


I would never be so bold as to say it's impossible but I have more faith in peoples ability to lie after an accident than I do in the ability of a reduced charge of 4831 to blow up a 270. I was just reading about this a few months ago on another forum where someone had an accident and everyone was talking about how this can happen. A week later the individual admitted that he had accidentally loaded the rounds with the wrong powder. He grabbed a can with the same color label and thought if was the correct powder. I believe he is in the minority that either realize they made a mistake or admit to it.
I have never seen a real study that was able to reproduce this. If someone has and can send me a copy I'd be happy to take a look at it.

Your quarrying example makes sense. Like I said, my examples were oversimplifications. Lots of things come into play. The fact that you stated it "shattered" along the fault lines is what I was alluding to. Things will usually break along the weakest part. If that fault was not there it would behave differently. The old pineapple grenades break into large chunks because deep cuts are cast into them. Without them they would break into smaller more random pieces.

Joined: Jul 2012
Posts: 3,632
Likes: 4
Sidelock
**
Offline
Sidelock
**

Joined: Jul 2012
Posts: 3,632
Likes: 4
dearmer,
I can agree with your faith in the ability of people to cover up for an accident; but when I had to reduce the speed of lightly constructed 22 HP bullets in my 5.6X61R vom Hofe to 3000 fps, so it would group, I still changed from 4350 to 4895 rather than endanger an heirloom rifle.
It's possible some with ringed chambers could have this same ability; consequently my interest in the real cause and conditions, if any, for chamber "ringing". The point of the C4 story was " lesser" explosive worked while the High explosive didn't. It was OK though, the purpose of the quarry was for training( even though we did use the rock, training other troops) and that provided a good lesson.
Nike

Joined: Dec 2011
Posts: 757
Sidelock
**
Offline
Sidelock
**

Joined: Dec 2011
Posts: 757
dearmer, thank you for taking the time to post your educated views. Too often we hear about something fourth hand or a reasonable ( on some level) story is repeated to the point it is taken as gospel.

Page 5 of 5 1 2 3 4 5

Link Copied to Clipboard

doublegunshop.com home | Welcome | Sponsors & Advertisers | DoubleGun Rack | Doublegun Book Rack

Order or request info | Other Useful Information

Updated every minute of everyday!


Copyright (c) 1993 - 2021 doublegunshop.com. All rights reserved. doublegunshop.com - Bloomfield, NY 14469. USA These materials are provided by doublegunshop.com as a service to its customers and may be used for informational purposes only. doublegunshop.com assumes no responsibility for errors or omissions in these materials. THESE MATERIALS ARE PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANT-ABILITY, FITNESS FOR A PARTICULAR PURPOSE, OR NON-INFRINGEMENT. doublegunshop.com further does not warrant the accuracy or completeness of the information, text, graphics, links or other items contained within these materials. doublegunshop.com shall not be liable for any special, indirect, incidental, or consequential damages, including without limitation, lost revenues or lost profits, which may result from the use of these materials. doublegunshop.com may make changes to these materials, or to the products described therein, at any time without notice. doublegunshop.com makes no commitment to update the information contained herein. This is a public un-moderated forum participate at your own risk.

Note: The posting of Copyrighted material on this forum is prohibited without prior written consent of the Copyright holder. For specifics on Copyright Law and restrictions refer to: http://www.copyright.gov/laws/ - doublegunshop.com will not monitor nor will they be held liable for copyright violations presented on the BBS which is an open and un-moderated public forum.

Powered by UBB.threads™ PHP Forum Software 7.7.5
(Release build 20201027)
Responsive Width:

PHP: 7.0.33-0+deb9u9 Page Time: 0.048s Queries: 27 (0.014s) Memory: 0.8367 MB (Peak: 1.8990 MB) Data Comp: Off Server Time: 2021-02-27 06:09:39 UTC
Valid HTML 5 and Valid CSS