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Photograph number 7 shows a loaded, unfired round from the shooters ammo box. There is a bulge in the case neck that likely had nothing to do with the failure but it does show that the reloader was not very picky or careful with his reloading process. Maybe he was equally lax about checking his cases for double charging. Tom
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05-11-2015 10:21 PM
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Interesting and scary. I found no information for A2520 used in the 6.5 X 55. I know that the loads should be kept in the 40,000 to 45,000 range. I did find data for the 6.5 X 47 Lapua that uses A2520 with pressures in the 60,000 range. Possibly the reloader read the wrong data. Also the Norwegian Krags are not as strong as the Mauser of the same caliber. The Swede Mauser data shows 55,000 as a limit and if the rifle was subjected to those pressures over the years it is likely the receiver became stressed. The barrel held up very well except in the area of the extractor where gas washing is present. I am a bit disappointed that more tests were not done on the ammo and using a 10 round weight average gives me pause to question. Since the ammo was poorly assembled with areas where extreme expansion would occur is also a point of consideration. I wish the actual reloading data manual was made available and the reloader could point out the specific data used. The bullet diameters are not listed nor is the weights. Could a heavier bullet found it's way into the mix? It may be that the powder used did not fill the case to the correct capacity, but if the loads for the 6.5 X 47 were used instead then that opens a whole new area of concern. This is all just speculation on my part.
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"The evidence observed provides support to failure being as a result of a single overload event; however, the upper part of the receiver ring was not recovered after the failure and as such could not be examined. It is therefore not possible to exclude that this section of the action did contain an flaw that led to the catastrophic failure of the rifle."
Sounds pretty wishy-washy, doesn't it? "There's a bit missing, so let's hypothesize that that was the cause of the trouble, and nobody can prove us wrong."
Well I'm going to stick my neck out, in the hope of seeing some though-out replies:
Barrels are proofed by themselves, before being used to assemble a barrelled system. So a "healthy" barrel should take a service load, even a proof load, without requiring any extra support from the receiver ring. Otherwise take-down systems would be totally unsafe. Yes?/No?/Maybe? And this barrel remained intact.
The remains show that the violently excessive pressure vented at the back, between the bolt face and the back end of the chamber. That this was sufficient to shatter the receiver ring suggests a detonation, not a plain gas expansion, as rifle systems are designed for safe venting of gas from a ruptured cartridge. The shattering of the receiver ring was the RESULT of the detonation, NOT ITS CAUSE.
I have said this before, but it stands repeating: anyone who says he wants a "hot load" is IMHO exhibiting a dangerously irresponsible mindset and has no business reloading for old service rifles. Or any other gun, for that matter. But OK, so I am conservative in such matters - shooting guns up to 200 years old, one has to be.
Last edited by Patrick Chadwick; 07-23-2015 at 06:43 AM.
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Thanks Trap4550 for a detailed answer. Rereading the NRA report I realize that I may have been a bit harsh on the reporters. They did not suggest that a possible receiver defect was the cause of the catastrophic overpressure, but that it may have been instrumental in the shattering of the receiver ring. However, the valuable link provided by BMF shows that this speculation is a bit of a red herring, as any ring is going to fail at the weakest point, and that is going to be at the location of the extractor cutout.
I still consider the report to be less than precise, and suspect that "D" may have revealed something in his submission that would have been useful for our discussion. Not that it is our place to pass official judgement , but it is appropriate that we consider this "food for thought" and caution others who may be led into temptation. And the temptation may be a combination of the following elements:
1) Using a powder in a cartridge/bullet combination for which there is no proper data???
This does not appear to be the case. The Accurate Reloaders Guide for 2005 (I do not have a more recent version) does indeed show 34.0 gn of A2520 as a maximum load for a Swedish 6.5x55 with a 140gn bullet.
2) Load too hot for the specific rifle???
The above load is shown as the maximum load for a 6.5x55 Swede with a 140gn bullet. So it was not a sub-minimum charge. Instead, rather too hot for a Krag.
- A probable contributing factor
3) Seating the bullet too far forwards??
I have read of people claiming to set their bullets 0.001" off the lands - implying that they can achieve a tolerance of +/- 0.0005". Putting it very politely, I find this hard to believe. Real-world variations of bullet ogives and case necks will hardly allow such a tolerance to be achieved, resulting in some bullets being forced into the lands, with resulting variation in pressure. And some people like to seat the bullets slightly into the lands in the quest for accuracy. But this raises the pressure significantly (and unpredictably).
- A possible contributing factor
4) Excessive neck tension** (or overlarge bullet)???
Now the bulge shown in the single case presented in the report can hardly have occurred in a loading press, as the neck section of the die would have prevented it. In case where, for instance, the bullet is too large or the neck is to tight, the typical result is that the shoulder of the case collapses.
BUT if you take a cartridge with the bullet set too far forwards, AND with sufficient neck tension that it cannot slide back, AND try to force it into the chamber, the result will look like the example in the report.
- A possible contributing factor
I have seen enough mess-ups on the range to suspect that the bulged cartridge shown in the report is one that "D" tried to force into the chamber, and then removed. I suspect that if we could see all the cartridges, there would be others showing this bulge, and that "D" simply tried until he found one that he could force into the chamber - and pulled the trigger. And did this more than once. With the results we have seen.
Of course, we do not have all the evidence, and will never know. But we can and should advise others not to make the hazardous mistakes listed above.
** For instance: a heavy crimp
Last edited by Patrick Chadwick; 07-25-2015 at 12:50 AM.
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Hmmmmm, First off at least no one suffered life threatening injuries, to me pic 4 the rusty part along the fracture and paragraph 18) (marks on the receiver) says it all, I very much doubt it was a reduced load but more a hot load with the instigator probably a hairline crack or a fracture caused by the re-barrel (could of been any of the steps, removal or fitting of new) was the initial cause the marks commented in Para 18, this looks like the cowboy hat and saloon doors were in full swing at the time of the re barrel.
The barrel threads or the start of them are not square and look like they may of be cleaned up or cut incorrect or adjusted to fit. also the machining of the first threads in the receiver, there is also signs of Galling.
A final thing I wonder when it was last headspaced ?
Looking at a Krag receiver (have one to hand) they are thin on the ground regarding material, as Trap4570 points out regarding pressures between the .30-40 and 6.5 x 55 having a quick look at a loading book there is a 10,000 difference between the two.
The other thing that I think is more stress on the receiver due to the target barrel fitted, I,m sure the original barrel would have had plenty of support.
Originally Posted by
Patrick Chadwick
- A possible contributing factor
I have seen enough mess-ups on the range to suspect that the bulged cartridge shown in the report is one that "D" tried to force into the chamber, and then removed. I suspect that if we could see all the cartridges, there would be others showing this bulge, and that "D" simply tried until he found one that he could force into the chamber - and pulled the trigger. And did this more than once. With the results we have seen.
Think what Patrick says hits the nail on the head.
Someone mentioned a method of crack testing. There is a simple and cheap way of crack testing, the most used method in the industry which I,m in is the dye penetration method.
Consisting of three cans of spray, a cleaner, a dye and a developer.
Although nothing to do with the above I have set aside a selection of Downloaded ammo for a future trip to the proof house, these are calibre's I shoot using pistol powder etc, it will be interesting to go through the results once submitted, its more or less to show the pressure ranges between standard loads and downloads, I,m hoping to write a full article on the subject and will have all the info to hand, but before I post it, I will submit it to the HBSA for publication (if they wish).
The other reason behind this is more to do with armchair shooters who quote facts and figures to me when I mention my downloaded ammo. 100% its what they have read on the internet........ its an amazing thing the internet but it does have its downside, I may be totally wrong regarding what I load and shoot, but have never soiled the pants yet and the teeth don't rattle as much as they do with normal loads.
Last edited by bigduke6; 07-25-2015 at 05:28 AM.
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Pat, I'm glad you were able to find loading info for that powder. I was looking at current data and the powder is not listed anymore for that caliber. I wonder why it was dropped. But that would be another dead end investigation. There is so many unanswered areas that I guess we can form our own conclusions as to why. My own rule with century old arms is to respect their limits. One caliber that comes to mind is the 8mm round and Remington loads this ammo. I'm sure they have done extensive research on the variance of bores as in .318 to .323 and found a load that is safer should a round find it's way into the chamber of say a Model 88 Commission rifle. I am always interested when a ruptured firearm comes to my attention especially when it is a old firearm. The rolling block comes to mind because it is touted to be a strong action of the period and I have seen receiver failures. On the opposite side of the coin, I read of a test to see what a trapdoor could stand. Numerous barrels fitted to a receiver and finally the barrel separated from the receiver with a 300 Win Mag from stripping the threads. It proves nothing in the end. Some of the statements may even lead to a false sense of safety. I totally agree with your posts. It is up to the owner to be responsible for his own and others safety and not rely on the firearm to be able to provide that safety.
Last edited by Trap4570; 07-25-2015 at 12:26 PM.