Kimber Swede Near-Catastrophic Failure

[Dutchman]

These photos below are the only ones I have for this incident. The receiver ring wasn't blown off but was bulged. There is a disturbing similarity between these two rifle accidents.

Hornady 3rd edition: 160 gr round nose using IMR4064: 31.6 grs minimum. 35.2 grs maximum.

In both these incidents the load level was nominal and in no way "hot".

Let us accept the owner statements as fact and work within the parameters reported and not speculate outside with unknown factors. I feel the answer is within what has been reported with both these rifle failures.

********************************************

* Kimber sporterized M96 , 1915 vintage.

* Hornady 160 grn interlock over 32 grn IMR4064, Federal primer, and remington brass on their 4th cycle.

* I did not notice any bolt stickiness or extraction issues.

* The stock broke at the wrist, under the floorplate, and just in front of that area, The trigger guard was slighty blown out and the receiver, even though it held, was misaligned. The extractor flew off in two peices, the ejector went, the floorplacete blew out.

* I am not sure if the problem was detonation due to a very light load ( hodgdon said it couldn't happen ) or a problem with the brass ( remington looked at it and said it looked like a failure caused by an overcharge). My other rounds of 160 were not overloaded after I broke them down.

* The case blew at the head and lost about 1/4 of it. The bolt head lost a portion of the raised radius that aligns the case. That part actually looked like an old fracture.

* I check each filled case with a flashlight on the loading block

* (a full case of the powder)....it would have been about 42 grains or so. Hogdons rep didn't think that would have created this much damage.


* I am leaning toward a too light load causing detonation, even though Hodgdon was emphatic that this powder would not cause this.
Other thoughts are too much neck tension caused by me not annealing or dirty case necks..though this is a stretch. But, the other 160 grain bullets did not come apart easily at all. It took quite a few vigorous whack with the intertia puller. I don't crimp the necks.
The other confesstion, is that my loading log book showed 34 grsn for that batch. My cartridge box sticker showed 32 grains. That discrepancy is haunting as well.

* 1.The receiver WAS damaged, but it was intact. It is very slightly bowed on the right side, just enough to prevent a replacement bolt from being inserted more than about 1 third of the way. I will put a caliper on that receiver and one of my others when I get a minute.
The trigger guard was similarly bowed out a little on the same side.

* Funny you ask about that batch of brass. In the same bag, there was a malformed case where the brass had a melted look. It was obviously un-usable.I sent that one along with the blown case to remington, suggesting that there may be a quality problem.
They said it was " not related", and sent me $10 as a consolation prize.


http://images27.fotki.com/v966/photos/2/28344/1676633/DSC_0301e-vi.jpg

http://images54.fotki.com/v1616/photos/2/28344/1676633/DSC_Bolt21-vi.jpg

[MtGun44]

Brass flow on the case indiciates pressue high enough to exceed the yield stress of the
brass. If brass was soft due to insufficient cold working or excessive annealing somehow,
this could happen with a normal pressure round. If the brass hardness is normal and
there was no mechanical defect in the brass (thin base, thin wall, lap in the metal, etc)
the only remaining factor is overpressure. I will not speculate on the mechanism of
overpressure. I tend to think that detonation of modern rifle powders is a fantasy, but
that is an unsupported opinion. My view is that claims of detonation without actual
measured, repeatable, chamber pressure data carry just as much authority as my
opinion - near zero. Hodgdon has modern piezo pressure systems and if they say it
cannot happen, I would suggest that we look elsewhere.

Possibilities would seem to be:

-- normal brass hardness, brass dimensional/shape defect - normal pressure load
-- soft brass, normal dimensioal/shape parameters - normal pressure load
-- normal brass hardness, normal brass dimensional/shape parameters - overpressure load

I would want to section and hardness test some more samples of that batch of brass.

Bill

[NHlever]

Since you have the case pretty much intact perhaps you should check to see if the bullets you are using still fit in the fired case. One guess is that the neck of the case couldn't open up enough to release the boolit before the pressure built to dangerous levels. I sometimes have been guilty of shooting loads as long as they would chamber, but we really do need to know how much the case can expand when we are using boolits that are over bore size.

[Dutchman]

Possibilities would seem to be:

-- normal brass hardness, brass dimensional/shape defect - normal pressure load
-- soft brass, normal dimensioal/shape parameters - normal pressure load
-- normal brass hardness, normal brass dimensional/shape parameters - overpressure load

I would want to section and hardness test some more samples of that batch of brass.

Bill

I agree that the brass is the most obvious factor at this point. With both shooters mentioning finding defective brass in their lot this would be the first place to begin investigating.

Dutch

[Larry Gibson]

I have to disagree on the idea that it was defective cases. On the head of the case look at the very enlarged primer pocket and the heavy brass flow into the ejector slot. Those are from obvious pressure over load. A defective case that splits or ruptures in the web/case head simply ruptures and does not exhibit those two obvious signs of excessive pressure. What it does show is classic indications of an SEE as mentioned in the other thread.

Larry Gibson

[madsenshooter]

In doing some primer pocket uniforming, I've noted that Remington brass is not as hard as it used to be. Had some recently made Krag cases, and some old once fired UMC cases. The stop collar left marks on the headstamp of the new cases, didn't leave a scratch one on the older UMC cases.

[MtGun44]

IMO, if the brass is soft with a normal pressure load, it would be visually identical to
a normal brass case with an overpressure load. I do not think there is any way to
see the difference in those two possibilities.

Given the bad brass in the lot, I want to know more about the remaining brass.

Bill

[Dutchman]

IMO, if the brass is soft with a normal pressure load, it would be visually identical to
a normal brass case with an overpressure load. I do not think there is any way to
see the difference in those to possibilities.

Given the bad brass in the lot, I want to know more about the remaining brass.

Bill


:drinks:

[Multigunner]

I'd just finished reading an American Rifleman article from 1986, and a very similar blown case head incident was described, the rifle a 788 in .30-30.
The cause in that instance was insufficient neck clearance. The load was an oversized cast boolit with a full power charge, no room for a double charge.

A case with a thicker than normal neck, or a chamber neck constricted by hardened fouling might cause such a casehead failure.

Since having had pressure signs (flattened primer and stuck case) with medium pressure loads, and those pressure signs going away after throughly cleaning the chamber neck using a homemade brass scraper, Chamber neck clearance is now the first thing I check with older milsurp rifles. Military powder often contain non energetic additives that, along with case mouth sealants, can build up into a very hard to remove layer that looks to the naked eye to be no different in appearance than the chamber wall.

[truckjohn]

I owned one of those rifles in 308 about 5-years ago.... I didn't like it... It wasn't particularly accurate with *Anything* I shot in it... It seemed to me that the small ring action wasn't really up to the task like it should have been....

On the chamber dimensions - that Kimber chamber and bore was pretty tight.... I was always amazed it didn't do better than it did.

Thanks.