March
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 29 30
31
Who's Online Now
4 members (Researcher, Jimmy W, SKB, arrieta2), 786 guests, and 4 robots.
Key: Admin, Global Mod, Mod
Forum Statistics
Forums10
Topics38,374
Posts544,009
Members14,391
Most Online1,131
Jan 21st, 2024
Previous Thread
Next Thread
Print Thread
Page 7 of 10 1 2 5 6 7 8 9 10
Joined: Jul 2005
Posts: 7,065
Sidelock
***
Offline
Sidelock
***

Joined: Jul 2005
Posts: 7,065
Why would an obstruction cause an over pressure in the breech down in the steel hull base? The case seems pretty strong that we had an over pressure because the primer was raised and the extractor was imprinted on the steel base.



I am glad to be here.
Joined: Feb 2003
Posts: 4,033
Likes: 45
Sidelock
**
Offline
Sidelock
**

Joined: Feb 2003
Posts: 4,033
Likes: 45
We're thinking that's an effect of the obstruction Mike, (as is the bulge) and not a result of a high pressure condition initially in the chamber.

Certainly the result is a huge pressure spike, and that's pushing everywhere until the rupture and big vent off.

Joined: Feb 2009
Posts: 7,444
Likes: 204
Sidelock
**
Offline
Sidelock
**

Joined: Feb 2009
Posts: 7,444
Likes: 204
Just the primer raised up by itself may not mean an over pressure situation caused it. Usually, snapping of a primer on an empty case or hull will raise the primer. It seems though that some condition allowed the primer to partially lift without being subject to the full pressure of the load, otherwise I'd think the primer might have flowed more or maybe perforated like they do now and then.

Joined: Jan 2006
Posts: 9,398
Likes: 307
Sidelock
***
OP Offline
Sidelock
***

Joined: Jan 2006
Posts: 9,398
Likes: 307
Been measuring my digits to numbins' and here goes.

1. I examined 19 empties + right chamber empty
No missing pieces inside nor out
The primer of the blow-out shell is similar to the others
NONE of the empties showed the extractor imprint found on the blow out shell



2. The entrance to both chambers measured .818". Hunter Arms specs is .809" so it's possible the chambers could have been hones slightly?

3. The piece wall thickness



The section which is the forcing cone (superiorly) was .123"
3/16" past the end of the forcing cone was .105"
The MWT was .094"

4. Around the edges of the blow out



5/8" from the breech at the apex of the blow out .150"
At the bottom 1 1/8" from the breech .130"
Moving along the bottom and the front was uniformly .121" to .123"
At the top, 2 5/8" from the breech .119"
The thinnest section was at what I believe to represent the apex of the bulge from 2 1/2-2 1/4" from the breech and was .110"
1 1/4" from the breech .122"
1 1/8" from the breech .126"

My assessment is that even with the likely elastic deformation with the bulge, all wall thicknesses are adequate.

Last edited by Drew Hause; 02/06/14 06:39 PM.
Joined: Feb 2006
Posts: 3,720
Likes: 48
Sidelock
**
Offline
Sidelock
**

Joined: Feb 2006
Posts: 3,720
Likes: 48
Drew, great work. I agree with your analysis of the wall thickness readings.


David


Joined: Dec 2001
Posts: 775
Sidelock
***
Offline
Sidelock
***

Joined: Dec 2001
Posts: 775
Let me add another possible cause of over pressure and a bulge at the point seen. A hang fire can cause something similar. I once had a click-bang hang fire while shooting skeet with a 28 gauge gun, or more accurately, Briley 28 gauge tubes in a 12 gauge Beretta 682. I had reloaded some hulls from a shoot where I had been caught in the rain, and I theorize that one shell still had a drop of water in it that delayed the ignition of the powder until it was at the front of the chamber, where it fully ignited. The result was a ring in the subgauge tube just forward of its joint with the stainless steel chamber. I continued to shoot until the match was finished with the bulged tube with no ill effects. There could be numerous causes for such a delayed ignition, other than a drop of water, but the result is the same, a localized pressure excursion that might be sufficient to cause the damage seen in this case.

Last edited by Tom Martin; 02/06/14 09:00 PM.
Joined: Mar 2002
Posts: 1,815
Likes: 4
Sidelock
**
Offline
Sidelock
**

Joined: Mar 2002
Posts: 1,815
Likes: 4
I loaded a double load of 7625 48 grs ! In a federal paper hull using my posness warren. I still don't know how i didi it, but i do remember the recoil. No damade to the gun , but it was hard to open and the primer was real flat

Joined: Jan 2006
Posts: 9,398
Likes: 307
Sidelock
***
OP Offline
Sidelock
***

Joined: Jan 2006
Posts: 9,398
Likes: 307
IN SUMMARY I'll start with a copy of the usual response from the ShotgunWorld Reloading Forum:

"A Damascus barrel is NOT as strong as steel barrel of the same thickness. Think about how a Damascus barrel is made, there are seams and voids all over it. If you don't believe me have a damascus barrel magnafluxed or x-rayed."

That was not the finding of the 1891 Birmingham Proof House Trial
Please review, and note that Whitworth, Siemens-Martin, and English “Superior Barrel Steel” were tested

http://docs.google.com/document/d/1dnRLZgcuHfx7uFOHvHCUGnGFiLiset-DTTEK8OtPYVA/edit
http://docs.google.com/a/damascusknowled...2Hx4/edit?pli=1

MagnaFlux or PD testing shows defect on the surface, not what is happening within metal.

The primary motivation in analyzing this barrel blow up is to apply modern testing, possibly including SEM, fully recognizing that one more than 100 year old barrel does not represent a statistically significant sample.
I will be meeting Monday with a Metallurgist at METL http://metl.com/services/ to explore analysis options, and if anyone here is interest in something other than BS, they might keep an eye on the DoubleGun thread...or not if more comfortable with mythology
http://www.doublegunshop.com/forums/ubbthreads.php?ubb=showflat&Number=356377&page=1

I do appreciate the statements made here regarding the near impossibility of loading a double charge of powder without evidence thereof with visual inspection of the shell/crimp.



What can we say with certainty:
1. The wall thickness of the chamber and barrel wall are adequate

What can we say with confidence, but still only as an (educated) opinion:
1. A powder overload was unlikely
2. The fracture/blow out did not occur along ribband weld lines
3. There is evidence of a bulge, and a bulge means an obstruction

As Mike shared (and thanks again)
Major Sir Gerald Burrard, The Modern Shotgun, Volume III, p. 415:
"In the case of an obstructional burst the really essential evidence is the ring bulge. If there is a ring bulge, there must have been an obstruction; and the absence of a ring bulge is conclusive proof that there could not have been an obstruction."

4. The extractor indentation upon, and expansion of the steel shell head, can be explained by the pressure increase prior to barrel rupture

Anything else?

And the prize goes to James Flynn who made the correct diagnosis back on Jan 27 smile

Monday I will be discussing:
1. composition analysis to see if we can determine a modern equivalent to the iron and steel used in fabricating the barrel
2. the best procedure to evaluate the barrel wall for 'seams and voids', inclusions, and micro-fractures.
3. If there would be any value in PD testing.
4. AND THE MOST IMPORTANT QUESTION - how may we best evaluate the integrity of our pattern welded barrels using non-destructive testing????


Joined: Dec 2001
Posts: 3,960
Likes: 89
Sidelock
**
Offline
Sidelock
**

Joined: Dec 2001
Posts: 3,960
Likes: 89
Here is a Remington Gun Club loaded with the exact data of the blown gun:

17.5 gr Clays DOUBLED to 35 grains
Downrange clone of Winchester WAA12L wad
1 ounce shot

Wad pressure on my MEC 9000 ran up to about 40 lbs
The hull would not hold the entire shot charge--about 1/16 oz ran over



When an old man dies a library burns to the ground. (Old African proverb)
Joined: Dec 2010
Posts: 239
Sidelock
***
Offline
Sidelock
***

Joined: Dec 2010
Posts: 239
Originally Posted By: Drew Hause

Anything else?


Something I've never seen discussed at length is, notwithstanding adequate wall thickness etc., can metal fatigue be an overlooked factor in old doubles? Metal fatigue is usually not detectable to the naked eye or through caliper measurements. Yet military research (albeit that research has been mostly done on very, very big guns) has clearly established that metal fatigue in such guns is real and that the safe and useful life of a gun has its limits, even if that gun was always operated within its design specs. Formulas have been developed to predict when a military gun needs to be taken out of service.

Page 7 of 10 1 2 5 6 7 8 9 10

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 - 2024 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+deb9u11+hw1 Page Time: 0.098s Queries: 35 (0.068s) Memory: 0.8681 MB (Peak: 1.8988 MB) Data Comp: Off Server Time: 2024-03-28 23:42:08 UTC
Valid HTML 5 and Valid CSS