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Interesting old thread here regarding steel strength

http://www.doublegunshop.com/forums/ubbt...&PHPSESSID=

Steel Type Max (lbs/sq in)
Damascus ------- 31,291 to 52,626
Typical 1905 Steel -- 64,000
Winchester Steel ---- 39,400
Winchester Nickel --- 88,600
Krupp Special ------- 85,340
Krupp 5 M ----------- 92,450
Bohler Antinit ------ 116,630

Great thread, the education has been so helpful!!

OH BOY! TEAM has already finished the MPI and radiography on the Smith No. 0 barrels with the bulge, and I'll be meeting with the metallurgist Weds. am.

AND I'll take this barrel for radiography of the bulge and normal barrel. Smith 4E Chain Damascus with a left barrel bulge from .735" at 3 1/2" to .758 at 4 1/2" with a minimum wall thickness at the bulge of .077 compared to .090 on the right. There is also a segment from 12" to 6 1/2" from the muzzle with a MWT of .016 on the left.



The barrels are unusable, but as 4E barrels, it would not be unreasonable to fit full length 20g tubes to the barrels.

Burst or no burst, bulges seem to have an affinity for predictable areas. Hope they have interesting findings for you, and maybe trends start to emerge.

Several images. Obviously these have been resized but I have viewed the original digital images and they have excellent definition and resolution. Clearly TEAM is on uncharted territory as they also have found no published images of radiography on pattern welded barrels. They are of the opinion that MUCH more information can be obtained from radiography compared to MPI. The ONLY finding on MPI was an 'indicator' at the sauter.
Just like an MRI of a lumbar spine, the results require expert and experience interpretation, by human eyes and we will need LOTS more barrels (ie lots more $s ) to clearly establish what the images are showing, and possibly sectioning and photomicrographs to confirm (more $s)
One major issue is if the less dense areas within the barrel wall represent voids, slag, inclusions, etc. or it they are from the pits. The techs are going to correlate the images with visual exam using a bore scope and we should have the answer.
One myth we can slay now is 'the wall is nothing but a mass of welds, defects, inclusions'. The wall looks like solid metal; like any pipe.
So here goes gentlemen

Negative images highlighting the probably pits





Positive digital images

Likely tool marks when the chamber was extended. The linear marks are unlikely to be from low cycle fatigue, but that may require photomicrographs



Large arrow is solder at rib extension and barrel junction. Second arrow is the bulge and you can appreciate less wall thickness ie. less dense. Lower arrow is porosity in rib solder



Probably pits rather than voids, slag, impurities in the wall

Just guessing, but I'd think slag from welding or inclusions in the original material might show as circumferential elongated forms as that's the direction that the steel was drawn while being forge and welded.

If those roundish spots are pitting, I'd think they'd be easy to see. Maybe if the barrels look smooth, they could end up being possible hidden defects. Might be tough to tell though exactly where those spots are, and the bulge picture doesn't seem to have any of those funny looking spots around it.

Here is another to add to the mix --

http://parkerguns.org/forums/showthread.php?t=12809

I hate to add a discordant note to Drew's excellent work and his current working thesis as to the cause but Burrard describes the obstruction bulge as being caused by the momentum of the forward rushing gasses being stopped suddenly by the obstruction. That is, the momentum of the gases at the rear of the barrel causes the gases to carry forward into a high pressure zone at the obstruction and further raise the pressure and then the ring bulge results. Had the barrel wall been so thick and the obstruction so solid that no burst had occured and the gasses allowed to quit rushing about and then the pressure of the contained gasses measured that pressure would be much lower than the pressure required to deform the barrels and make the bulge. If it were not for the momentum of the gases near that are crashing into the obstruction that pressure would not go so high as to cause a bulge. Since the bulge occurred right at the forcing cones I don' think there was enough velocity for the gas momentum to cause a high temporary pressure large enough to burst the chamber. I think it was just an overcharge or an overcharge and a defect in the barrel.

I have become confused which barrel we are talking about on these various threads. I am talking about the damascus barrel that recently gave way on Drew's friend at the skeet field.

Thank you Dave; I totally missed that. Just so we keep the infro together in one spot, here are the images, and my response








By the appearance of the blow out, I think there is little doubt that there was an obstruction, likely at the forcing cone, and would suggest that you examine every empty used prior to the event for a missing base wad or piece of plastic. AND please check the shell that was in the chamber for expansion of the head, and an indentation on the head from the extractor. Because of the plastic deformation of the chamber, I am quite confident that this was not simply a fracture of the barrel wall.

A formal failure analysis costs more than $1000, but if you would like to send me the remains, I could measure the wall thickness around the blow out and also ask the Metallurgical Engineer at METL for his opinion. Possibly a visual exam of the edges would confirm my thoughts.
Also please send the remnants of the shell, or post an image of the head.
Another option would be destructive testing of the remains, with sectioning and photomicrographs. This is the big $s.

Wait wait wait!

Drew... these pix aren't of the Remington barrel that started all this.

This is a CHAMBER blow out.... a clear result of an over load.