[Redtip17]

Take a look at this wed Site> http://www.thegunzone.com/rifles-kb.html :down:

[Turtlenapper]

Moved to rifles :up:

[Popeye]

I see the rifle destroyed by a "moderate" handload. I don't see those supposedly destroyed by factory loads. Hmmmmm.

I'm not saying its not so. I'm merely saying hmmmmm.

[7.62mmFMJ]

Most KBs in Glocks are also from "handloads"

[Zircon]

Handloads, huh? A squib first round, perhaps, lodges one down the bore, followed up by a second "live" one. I dunno.

[Popeye]

He flashes those pictures too fast to let anyone get a really good look at the destroyed rifle.

[Redrum]

He flashes those pictures too fast to let anyone get a really good look at the destroyed rifle. Here ya go...

[Redtip17]

Even better pictures of this rifle can be seen here>> http://www3.telus.net/drswebspace/SAKO%20BLOW%20UP/

The above site shows the best pictures of the rifle. It seems that this was the 50th round fired thru the rifle. AND no there was no barrel obstruction, the 49th round was in the target and was verified by others at the range.

The problem lies within the Mfg. of the barrels. Seems Beretta changed the lubricant used in the hammer forging process and it caused stress cracks to form in the barrel.
Beretta says that if you have one bought after FEB 2004 DO NOT FIRE IT UNTIL YOU CONTACT THEM. They want to check the SN of it. Bill

[Zircon]

Ah, thanks, Bill, that starts to make some sense. "Me knows" lots about the rotary forging equipment used to make barrel blanks. My company has a GFM rotary forge, only it's much, much larger than the ones they use to make barrels (well maybe some good sized cannon barrels say 8" diameter x 30' long could be made on it.)

Here's the scoop as I see it, based on Redtip's info: The forge consists of four dies or hammers, radially aligned, at 90° intervals. The major diameter of each of the hammers can be adjusted inwards or outwards thus effecting how much reduction is taken. There are a couple of manipulators at either end of the forge. Their job is to feed the bar into the dies, and rotate it at the same time. The sequence is feed/turn/stop. During the feed and turn the dies are in the open position, and while the bar is stopped, the dies hammer the material down (and in the case of making a barrel, hammer it onto a central mandrel) in the radial (to the bar) direction.This can be done hot, warm, or in the case of some steels, cold. In the small GFM's the repetition rate is very fast - 100's of strokes per minute.

It is possible to get long, longitudinal seams with the rotary forging process through improprer process control. Parameters that have to be controlled include metal temperature, the area percent reduction of the bar for each pass, any lubricant that may be used (as in cold forging), surface condition of the bars prior to forging, the pass schedule (how much reduction takes place when in the sequence as the bar is passed back and forth between manipulators - one doesn't go from beginning size to final size in one fell swoop), and several other minor variables.

I do not have direct experience with cold forging or use of lube, but I can easily see how long longitudinal seams could develop if a major parameter such as lube was lacking. These seams are capable of running down the length of the forged part measuring in feet, not inches or fractions of inches.

The scenario goes like this: this surface of the bar being forged takes a real beating (no pun intended) by the direct contact of the hammers, or with contact of the ID mandrel. The configuration of the hammers (their geometry), and the softness/hardness of the metal at the surface can create lengthwise (longitudinal) laps or folds. I believe that lack of lube could sufficiently modify the interaction of the hammers with the surface to create these laps or folds. These folds then get burried under the surface with continued forging. This sets up an internal defect and as more deformation is departed into the bar, it can open up into a longitudinal crack. It's unusual to see just one lengthwise crack on a bar, there are usually several of them spaced around the circumference of the bar - just like what we see with the Tikka barrel. Remember that there are also two free surfaces here, the ID surface as well as the OD surface since the barrels are forged over a mandrel, so the crack could be near the OD, or near the ID.

The closeup photos of the fracture surface still aren't very good, but it almost appears like there was a pre-existing crack, and that there is evidence of fatigue failure. This photo, http://www3.telus.net/drswebspace/SAKO%20BLOW%20UP/SANY0016.jpg, is particularly interesting. Look at the lower barrel section, and on the lower half of the barrel, right at where the leade is (the area just downstream from the chamber.) There is a series of lines that radiate back towards a central point on the bore side of the barrel wall. These are indicative of fatigue cracks and where they point back is the origin of the fatigue initiation site. Based on this very limited evidence I would say that the barrel had three pre-existing, longitudinal cracks, near the ID surface, and that the barrel came apart right at the end of the chamber near the leade area. The cracks rapidly propogated down the length of the barrel. Once the barrel let loose, there was little that the receiver could do to hold it together and it split open as well.

Ugly, ugly failure. There's gonna be some law suits over this one.

[Redtip17]

Zirc,
My thoughts were that the rupture started within 1/4" of the throat. It looks to me like it radiates outward from this point, going both backward toward the chamber mouth and forward toward the muzzle.
If this fracture was pre-existing all the way to the muzzle then once it started to separate there was nothing to stop it from going all the way. It would follow the path of least strength. Like splitting a piece of bamboo lengthwise. Bill

[Zircon]

Yep, you read the failure signs well, Bill. The initiation point is as you indicated. Repeated loading of the barrel from firing caused incremental growth and arrest of the crack in a radial direction from the origin. I do believe, however that there had to be some longitidunal seams near the ID (or less likely OD) surfaces for the barrel to split lengthwise like it did. Otherwise the rupture overload would have just been concentrated near the chamber, and it is likely that, as the pressure was bled down, the crack would have arrested in ductile metal well before she went all the way to the end of the muzzle. Most of the damage is done in the breach area, even though it is thickest, owing to the high pressures developed in the breach before the bullet has chance to travel down the barrel and open up some volume to relieve the pressure.

Ain't failure analysis fun? I'll bet it wasn't fun holding that bucket of shrapnel when she let loose. We can do a lot of speculating based on some incomplete evidence, but some metallurgist with a scanning electron microscope will be tasked with figuring out the details based on the appearance of the fracture surfaces. Someone will then have to go back to the manufacturing process and look for possible causes. I've kind of sketched out what I think happened, but there is a lot more to it than just looking at a photo or two and making a conclusion. Still, I'd say we're not too far off.

[Redtip17]

Zirc,
Somebody just posted to the thread that I put over on RFC too. They said they had read of 2 others coming apart with factory ammo. AND they came apart in the same fashion. Barrel split into 3 pieces and receiver right down the middle.
I would expect the receiver to split down the center. That has to be the weakest part of the "Casting." You noticed that the receiver IS cast by the grain in the fracture. It has that broken grain look with no tears, just molecular separation. If it had been machined from a solid billet it might have contained some of the barrel separation at the threads. but "I doubt it." Cast steel is just not flexible, it just plain won't stretch like an extrusion will.. Bill

[Zircon]

Agreed, receiver looks like a casting. However, receiver was not designed to take the kind of overload that occured. The barrel is the primary pressure boundary. If it hadn't ruptured, the receiver would not have been an issue. As thin as that receiver is along the break, I doubt if a forged receiver or one machined from billet stock would have fared any better.

I don't get it, speaking of thinned out receivers. Manufacturers are chambering magnum rounds in 6 lb rifles. They pair away any excess steel down to the point of no extra margin at all. The rifle stays together if everything is perfect with the materials, the manufacture, and the ammo. Pretty difficult to have everthing perfect in this world, especially in 3 diverse areas, and the end result is a big KB like this one. Not only is the safety margin paired away, the recoil goes up big time also. Wake up "shooting public" this is the endgame for your desire for 6 lb magnum rifles!!

[Popeye]

Thanks for the pictures and commentary. Most interesting. I'm glad all my Sako rifles are pre-Beretta.

A six pound Magnum rifle? You have to be a pain lover to use one.

[Zircon]

A six pound Magnum rifle? You have to be a pain lover to use one.

Yep, precisely the point. In more ways than one. Pain from recoil. Pain from the damn thing blowing up in your hands. :down:

[Plinker]

Scary stuff.

Fellow I worked with,back in the eighties was killed when his rifle blew up. Didn't do anywhere near the damage to the rifle as shown in the picks.

[Tony]

Usually when barrels come apart like that it is from unseen flaws in the barrel steel. When I was working at Barrett Firearms, we had 3 barrels blow just like that. It was later found out that Krieger was using seamed material instead of ordnance grade bar stock.

I had fired one rifle and on the 3rd shot it came apart. The barrel looked exactly like the pics. After a weeks time, 2 more rifles came apart like that. We x-rayed the rest of the lot and found 4 more barrels with interior flaws. We returned the barrels and started x-raying all barrels.

It isn't fun to be behind a .50 BMG when the barrel blows. On the second rifle I had to go to the hospital because I thought my collar bone was broken. It was a bruised bone.

[Zircon]

Tony, at least Barrett was doing some non-destructive testing (X-ray) to try and sort out problems. I wonder if Tikka was doing any NDT at all? Eddy current bobbin-probe down the ID, or ultrasonic examination of the barrel blanks?? I'll bet I already answered my rhetorical question.

You had three .50 BMG barrels blow on you? Damn!! After the first one (if I survived) I'd have been behind a concrete block wall with a long string attached to the trigger. .50's are just plain nasty to fire, even when they're working perfectly. Not so much the recoil, but the pressure wave/concussion that I don't like.

Can you describe the flaws in any more detail? Shape, location, possible origin? When you say Krieger was using "seamed" material what exactly do you mean? Was this material that had seams as the result of bar rolling? One can certainly get longitudinal OD seams from a hot bar rolling process (the process used to make the majority of hot rolled, round bar products.)

[Tony]

Yes, Krieger had used some rolled stock. It was supposed to be drawn bar stock, but Krieger said they couldn't find any at the time and thought it "would be all right".

Yes, .50's have one mean bark. I had to finally stop shooting because of all the rounds I had fired while working there.

The flaw ran longitudinal to the long axis of the barrel. After they split, you could see the seam. Where we had parkerized the barrel, you could see where the park solution had seaped into the material.

[Zircon]

Yes, Krieger had used some rolled stock. It was supposed to be drawn bar stock, but Krieger said they couldn't find any at the time and thought it "would be all right".

Yes, .50's have one mean bark. I had to finally stop shooting because of all the rounds I had fired while working there.

The flaw ran longitudinal to the long axis of the barrel. After they split, you could see the seam. Where we had parkerized the barrel, you could see where the park solution had seaped into the material.


OK, that makes sense. OD longitudinal seams from bar rolling. When the rolling process is done the bar goes from a squashed oval shape back to a round, each shape getting smaller in cross-sectional area as the bar continues through the multiple reduction stands in the bar mill. During the rounding up process, the bars can "wrinkle" on the surface and this causes longitudinal seams. If sufficient "meat" isn't removed from the OD of bars during subsequent machining they can stay in the finished barrel as very tight seams or cracks running lengthwise. Since the parkerizing solution got down into the seams, an obvious (and cheap) quality control measure for Barrett would have been to use ultraviolet visible dye penetrant to test for the presence of OD cracking. The dye would wick down into the tight seam, and then be drawn out by the talcum-like developer to have a very easily visible trace of where the crack was located.

This whole thing with barrel making is a bit scary, as we probe into it. A barrel is an extremely high pressure, pressure vessel. ASME (American Society for Mechanical Engineers) which has control in the U.S. for pressure vessel design, manufacturing, and certification, has extremely stringent NDT (non-destructive testing) requirements for pressure vessels like boilers, nuclear containment vessels, hydraulic accumulators, heat exchangers, compressed air vessels, and the like. I'm getting the drift that the rifle barrel makers don't do squat in the way of NDT, until perhaps they start having KB's and it's too late. Shame on them!