The load was 200 gr. Horn XTP'S with 27 gr. of H110.
More here.
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So far 100% of the KBs I've seen have involved reloads.
ReplyDeleteCoincidence?
Double charge.
ReplyDeleteActually, from the thread it look like _under_ charge was the fault(still reload problem), the powder used can't even be double charged(wouldn't fit in the case).
ReplyDeleteEnough charge to make enough pressure that it has to come out, not enough to move the bullet out of the way, apparently.
Anon:
ReplyDeleteIf you read the thread, he used 27gr of H110. A double charge won't fit in that case.
27 grains??? Holy freaking overload Batman! Thats nearly a double charge, of powder thats high pressure to start with.
ReplyDeleteI would like to see the piece that came off.
ReplyDeleteFrom the photos, it looks like you could place the broken cylinder on a flat surface and all four broken surfaces would touch the table.
it would be interesting to see whether the bit that came off is all bulged to hell, or if it has that same straight break. If it has the straight break, it might suggest a flaw in the metal the cylinder was made from
- they happen sometimes
but dodgy reloads seem much more common.
Keith
I don't know anything about reloading, so my comments are limited.
ReplyDeleteThe consensus on the thread seems be that he made a reloading error of some sort.
If I were S&W I'd want that gun back at the factory so it could be examined. Just to be sure that it wasn't a manufacturing defect. It would be worth their while to give him a brand new gun, just for the positive PR value.
carteach0, if you go to Hodgdon data site you will find that 27.5g is their recommended starting load. Best guess is either a faulty cylinder that failed or much more likely, a serous under load that caused a massive pressure spike. It happens, rare, but it happens.
ReplyDeleteGrendel
Carteach, per the thread, the IMR website calculated the load as being a little on the light side. They recommend starting at 27.5 grains of H110.
ReplyDeleteNow let me teach all of you something exceedingly important about the metallurgy of Aluminum Alloys. (This was an Aluminum Scandium Alloy gun.)
There is a thing in metallurgy called the fatigue limit. For steel it is generally 1/10 of yield strength (not UTS or Ultimate Tensile Strength). That means that you can stress the part to 1/10 of Yield forever and it will not ever form cracks. This is more or less true with (almost) all metals. The percentage of yield varies by alloy and alloy group, but they all have a value at which you can stress the part forever and never fail the part.
This is not true of Aluminum. Aluminum is unique in the metallurgical world in that it has no fatigue limit. There is no level of stress that when applied repeatedly will never fail the part. (Technically that is not true, some recent studies have found a fatigue limit that is around 1/1000th of yield, but that is so low as to be virtually irrelevant.) That is why aircraft are constantly inspected for cracking. Now the magnitude of the stress and the rapidity of the onset of cracking are related to each other more or less linearly, The higher the stresses, the quicker it will fail. But they will ALL fail eventually.
Additionally, Most aluminum alloys are "precipitation hardened" meaning that they are subjected to a special heat treating regime in which elements that are dissolved into the alloy begin to precipitate out of solution into the grains and grain boundaries of the crystalline structure. these act as "locks" to prevent grains from moving past each other during stress. The problem is that many of these alloys continue to precipitate these elements throughout their lives, especially when they are subjected to elevated temperatures for long periods of time. Eventually the grain structure is so full of these precipitates that the internal stresses of the grain structure are overcome and the grain structure ruptures, causing microcracks throughout the alloy. this leads to both intergranular corrosion, and the cracks can also marge to form larger and larger cracks.
Knowing what I know about the metallurgy of aluminum alloys. I WILL NOT OWN AN ALUMINUM GUN.
How is it possible to have an under-charge detonation with such a high-volume powder?
ReplyDeleteI always assumed light-charge detonation happened in BIG cases with small charges of powder.
Carteach - No, it's not. If you read the thread, thr starting loads seem to be right around 27.5. If anything, it was apparently an under-loaded round. (as others have stated)
ReplyDelete200 GR. NOS JHP Hodgdon H110 .429" 1.600" 27.5 1708 29,000 CUP 28.5 1806 37,800 CUP
ReplyDeleteH110 is believed to be subject to detonation when underloaded. Now while 27.0 is .5 under Hodgdon's start load, it is well within the range given in Hornady's 7th ed, which gives a range of 26.3 - 29.5 grains of that powder.
ReplyDeleteDouble charge is impossible with that powder.
6th round fired from that revolver. (Brand New). Most likely the first round fired from that chamber. I actually have to think that it was a defect in the grain structure of the cylinder.
Eh, it looks as though he's still got three good chambers, not to mention that the gun is significantly lighter than it was before, which was probably part of the reason he bought it.
ReplyDeleteWho fires reloads out of an airweight ? I'd be scared to even use +P factory rounds. Is it possible that it was something like a squib (similar to what mikael suggested), maybe due to a burr in the forcing cone or something like that?
that is CLASSIC detonation...notice the the REAR of the cylindar is "clean" and the rest is "charred" around the bullet/crimp area??
ReplyDeleteIts REAL easy to double charge a reload if you're not paying attention. In fact, my setup consistently throws a double charge on the first reload. Not sure why, but that powder always goes back in the hopper. Rest are 100%.
ReplyDeleteI'm not a reloader or a metalurgist, but I am a former factory warranty guy (not for firearms). I'd want that gun back just to examine for manufacturing defects. And no, I wouldn't give him a new one. If the design is sound, and proven in the field, and you trusst your processes then it's sound to question the use or applicaation. Just my opinion.
ReplyDeleteMike
329PD, eh?
ReplyDeleteI have two Ti-cylindered wheelguns (sold the 325PD) and they have one thing in common: While the rest of the gun gets cleaned like a regular firearm, the cylinder itself only gets a rubdown with a lubed cotton patch, and then only rarely. I live in mortal fear of disrupting the voodoo coating that prevents flame erosion and crack propagation in the titanium.
Rorschach,
ReplyDeleteIron and iron based alloys ("Steels") are the only commonly used metals WITH a fatigue limit.
In ALL other commonly used metals, you can plot stress against frequency and they will give a straight line graph for fatigue failure.
That is why aircraft parts are given a "Life" before they must be changed (inspection for cracks is still necessary though).
Precipitation hardening may not be taken to completion during the heating used to speed precipitation, but further precipitation will take place at normal temperature (as it would even without the heating, the heating just speeds the process) but the degree of phase change is limited by the availability of alloying elements to form the new phase. Once they are all in the new phase, the process CAN NOT continue.
Are you confusing precipetation hardening with the different process of intergranular corrosion that was a problem with old zinc die castings which contained lead as an impurity?
Fatigue limit for Iron based alloys is about 1/2 of yield stress.
Generally, a gun will not be fired often enough for fatigue to be a problem. wear or corrosion will be a problem much sooner. Something like an IC engine will give you the several million reversals within a few hours of running, and anything loaded above its fatigue limit will fail in that time. everything there is well lubricated and cooled so wear is not so rapid.
With guns (even machineguns) the max allowable stress on any part is the yeild stress, and a factor of safety of root 2 to root 3 is normally applied to allow for material and machining defects.
Casting and rolling flaws do occasionally occur, even in carefully prepared metals, and sometimes there is segregation of alloying or impurity elements, which leave a plane of weakness. Under many jurisdictions, these would be identified by firing with a proof charge.
I have my suspicions about this failure. It would certainly be interesting to know.
On page 337 of the 48th edition of the Lyman Reloading Manual we see that for a 180 gr jacketed bullet the MAX load of H110 is 14.5 grains. This guy was loading a heavier bullet (which takes less powder) at 27 grains, or almost exactly double the max published load...
ReplyDeleteOn page 337 of the 48th edition of the Lyman Reloading Manual we see that for a 180 gr jacketed bullet the MAX load of H110 is 14.5 grains.
ReplyDeleteYou must be reading that incorrectly. I looked at my collection of manuals for .44 magnum loads using a 200 grain JHP and find the following:
Hornady #4: 26.6 - 29.1 for the 200 grain XTP.
Hodgdon #26: 26-27 grains.
Speer #11: 25.5-27.5 grains.
So they were definitely hot, but nowhere near the degree implied by your post.
I'm thinkin' Les was lookin' at the .357 data...... I was thinkin' "That's a damned HOT load!", too, untill I figured out that it was a .44 ......
ReplyDelete