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October 16, 2017, 09:10 AM | #26 |
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Good post.
Whoever wrote the SAAMI piece was trying to do a public service, but was not a precise technical person. The page also states, for example, that powder contains enough oxygen to burn completely. Nitrocellulose combustion is actually oxygen deficient, which is why carbon is left in your bore instead of it all becoming CO or CO2 gas. The suggestion powder should be stable in the right conditions for decades is based on bulk powder. You buy a train-carload of powder in a single lot and, barring a process error, it will, indeed, last for decades under good storage conditions. But it will also have a burn rate that typically wanders 15% or so from one lot to the next (board member Hummer70 said that during his years as a test director at Aberdeen there was one lot of powder that was off 30% from nominal in burn rate, but that the most extreme example he'd seen, with 20% being the next highest). A 10% charge reduction doesn't cover it a burn rate change as wide as can occur in bulk powder, which is why you need a pressure test gun to determine loads with it. The canister grade powder sold for reloading has to have its bulk grade parent lot tested for burn rate at the powder plant and then adjusted by the plant to bring it within the tighter limits needed for published data to be reasonably valid for it. Hodgdon says they use control to ±3% for their Australian powders and ±5% for IMR powders. Those are probably as much as the particular plants can achieve at reasonable cost. The way they adjust the burn rate, as I mentioned before, is by blending with held-back prior lots that were unusually fast or slow. You get a new lot that is too fast and you blend it with enough of the slow held-back lot to get the burn rate close to nominal, and vice-versa. So when you buy canister grade powder, unless the new lot came out of the factory just happening to be already inside the canister burn rate window, then you are buying a blend of new and old powder with no knowledge of the age of the latter. In the case of your '98 and '99 N140, I'm guessing one year the base bulk powder lot was too slow and the other year it was too fast, so one was blended with a held-back fast lot and the other with a held-back slow lot to adjust the burning rate. The held back lot that went into the '99 was getting older than VV realized, and that caused the problem. The N140 lot problem has been, as you noted, pretty widely reported. Dumping it avoids the bore rust I experienced. My gun looked clean when I put it away for a couple of months, but when I next got it out the bore was lined with fine surface rust. No powder frugality is worth that. As to Buck's idea to adding new stabilizer to old powder, that is what the Olin spherical powder process was invented for. New stabilizer cannot simply be applied to the surface, as some deterrent coatings can. It has to be an intimate mixture throughout the substance of the powder. This means the grains have to be redissolved in solvent, the deterioration products washed out and neutralized with a carbonate until the pH is correct, and then new stabilizer added and new grains formed. During WWII there were aging stockpiles of artillery powder in linen canisters and other powders that were reaching stockpile their age limits. The Olin process was able to salvage the remaining good nitrocellulose in the powder for use in fresh powder. (See Hatcher's Notebook, pp 219-229). Heat and UV light (and higher energy forms of radiation) can cause powder to break down at an accelerated rate. Air, absent unusual humidity levels, will not, as there is a lot of air not only between grains of powder but in all partially filled containers. I have a small remaining quantity of Brigadier 4065 at the bottom of an 8 lb container where it has been since before Scott's rifle powder plant burned down over 20 years ago. It is still just fine and occasionally sampled for ballistic comparison, as it was a great .30-06 powder. On the other extreme, I recently opened a new, sealed, 1 lb container of the discontinued Accurate 3100 powder of about the same age as the 4065 and that had been kept in the same cool, dry basement. It smelled strongly of darkroom-like chemicals. No red dust or visible red gas fumes yet, but I immediately took it out to the garage before the fumes could find their way into another powder's container. Now that I've opened it, I can smell the odor even around the tightly closed lid. It will fertilize the lawn. No visible lot number, but its a modern brown HDPE container with red cap, and anyone else who might still have some of this old powder around should check it. Making up test loads with good smelling, red dust and fume-free old powders is no issue, as they go bad over a period of months and not minutes. Just don't load old powder too far in advance of making a ballistic test. On reflection, I think the main hazard in mixing old powder with new is the habit of doing it. Suppose you buy some canister grade single-base powder that was burn rate adjusted with a 20 year-old lot of held-back powder. You keep it 7-8 years so it is now has some 27 or 28 year old powder in the can. You mix it with your new powder, and then, when that batch is getting low, you mix it with the next canister you buy 7 or 8 years later, and so on. If you have a 30 year reloading life and keep that practice, it becomes possible to have some grains of nearly 60 year-old powder in your container. When I went to shool I majored in chemistry for a couple of years before switching to electrical engineering. We were taught never to return any chemical to its primary stock container once it had been dispensed. Rather, we always had to put any excess in a temporary working stock container that was labeled and dated. The idea was to avoid inadvertent contamination that could spoil the stored stock purity. I think that's a good practice with chemicals in general and gunpowder, specifically. I never return powder from a powder measure to its original container It has been exposed to light and possibly to different humidity, or maybe even a missed grain or two of some older powder has found its way in. I clean and keep and relabel old powder containers as working stock containers for this reason. The 3100 jar will be washed out with an acid-neutralizing cleaning agent like Formula 409 and final rinsed with distilled water, given a blank shipping label and put into working stock service.
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October 16, 2017, 09:19 AM | #27 | ||||||
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October 16, 2017, 10:30 AM | #28 | ||||||
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Military Surplus Powder autocombusting http://www.ar15.com/archive/topic.html?b=6&f=3&t=248538 Quote:
Cincinnati Kid Platinum Bullet Member Join Date Dec 1969 Location Cincinnati, Ohio Posts 421 Quote:
Old Powder Caused Fire! http://www.thehighroad.org/showthread.php?t=788841 ________________________________________ Quote:
This section is from the Dec 2003 Propellant Management Guide: Quote:
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October 16, 2017, 11:13 AM | #29 | |
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While I know I'm not immortal, I also know I didn't get old by being stupid, nor was it just dumb luck. I take reloading very seriously and try to use sound judgement, safe practices and reliable techniques when doing so. While my ways may not mirror others, they have worked well for me and proven safe and effective. Still folks need to use sound judgement to determine how they do things, and not just do what I do. |
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October 17, 2017, 10:46 AM | #30 | |
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I would emphasize the checking of powder at each reloading cycle is important because, when you buy a canister grade powder, you don't know if you have any 20 year-old powder in the container or not. It depends on what it was blended with for burn rate control.
I read that Hodgdon improved their QC system in the early 2000's because of problems with significant burn rate variations in some Varget lots that had occurred in the 90's. I don't know if the QC changes did anything about aging, but given the IMR4007SSC recall notice is from 2015, I am guessing that, as distributors, they don't control it that far up the line. The other thing that can go wrong with powder is someone letting it sit in a shipping container for too long. Appliances are usually rated to withstand 170°F for two weeks in their shipping boxes due to how hot those containers can become in some locations. The Navy and Norma tests done at around 140°F break down new powder in under two years. Getting it even hotter would rob powder of life expectancy fast. Quote:
In practice, hydrogen grabs oxygen to make water, first and foremost, which dissolves other gases, including hydrogen and nitrate radicals normally in aqueous nitric acid solutions. But stealing oxygen from nitrate radicals leaves some nitrogen dioxide behind. That's the red gas. It also dissolves in the water formed and in any water present due to humidity until the water is saturated, at which point it fumes off.
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October 17, 2017, 11:25 AM | #31 | |
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What cool dry place would they be storing this rather large amount of powder for 20yrs . Seeing how it's been 20yrs I'd assume they have even more 18 , 16, 14 , 10 year powders they are storing as well . Oh then there's ALL the different powders to consider they must be storing for many years , remember we're not just talking H4895 here . I'd assume there QC would be good enough to be able to mix those powders well before the 20 year mark to get the burn rate they are looking for . This is not to dispute the over all point being made but 15 to 20 year old powders being mixed with new powders to be sold as NIB powders does not sound like a good idea . EDIT I'd think they could just purposefully make a powder a tad faster in order to mix the slower lot that's been around a year or two with it . Then use that mixed powder as bulk grade powder rather then letting any powder sit around for many years .
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October 18, 2017, 09:27 AM | #32 |
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MG,
If they could make a faster or slower lot reliably on demand, then they would just make the bulk burn rate correct in the first place. A big part of the problem is the purity levels of the constituent chemicals would have to be higher to do that, and that can increase material cost ten or twenty fold pretty easily. I ran into this working with pentadecane as a phase change material for cold packs for vaccine transport twenty years ago. The technical grade stuff had almost twice the heat capacity and a much tighter melting range than the solvent grade, but it was $60.00/lb verses $2.50/lb, so guess what the plant needed to use? One results of cost and some process limitations is powders come out of the plant with a span of lot burn rates. The probability that any lot will have a particular burn rate will describe a bell curve with the target burn rate at the center peak. An attempt to intentionally make a faster or slower lot will move the bell curve center up or down the burn rate scale, but you'll still have a lot of overlap of the new and original curves. A lot you run with the new target rate using the usual materials and processes may turn out well inside the usual burn rate range in the end. You might have to make a number of lots that way to get what you want, and that would make the investment unattractive. I would need to pick the brains of someone currently in the industry to know, but based on the probability issue it seems likely that if you got an unusually fast or a slow lot making the powder the usual way, since you still have all the same costs of production for a lot that hit the target burn rate perfectly, you wouldn't want to lose that by just dumping it on the surplus market or absorbing the cost of reprocessing it. You could sell it to an ammunition maker as a special lot suitable for cartridges the powder type isn't normally used in, or you could set it aside to be used for blending at some uncertain pace in the future. I was in a lab last year which had state-of-the-art bench top rapid NMR Spectroscopy gear that gave a complete organic chemical profile of a food sample in about half an hour. Astonishing compared to when I was in school. If I were running a powder plant, I would run analysis on samples of a fast or slow retained lot to determine the remaining stabilizer content and judge from that whether to blend it with a new powder or not, and not use age at all. Age is, in this discussion, just a surrogate for stabilizer loss, and given the various recalls and my own experiences with powders that went bad in under 20 years, it doesn't seem to be an entirely reliable one. I'm sure no maker sells poor powder on purpose or stores it badly on purpose or gets bad raw chemical impurities on purpose. I'm sure, for reputation purposes, they would have every lot hit the target burn rate right out of the drier and then last indefinitely if they could. But the nature of the process and cost constraints won't allow that. The probability of breakdown initiating after a certain period will have its own bell curve.
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October 18, 2017, 11:26 AM | #33 | |
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Also, it is very poor practice to get in the habit of mixing powders. The "only one powder container on the bench at a time" rule was formulated for a reason. When someone thinks they are returning Powder "X" to its container, but inadvertently dumps it into a canister of Powder "Y" is how catastrophic accidents happen. Your original post said the existing canister is as much as 8 years old. Are you going to be using the new canisters at the same rate? If your pace of consumption isn't about to accelerate tremendously, by the time you use up your new canisters, some of the powder in them will be sixteen years old. And yes, the new canister has new stabilizers and anti-oxidants, but you can't assume they will "migrate" to the old powder you just added. Have I always followed that rule myself? No. Have I taken the remnants of a nearly empty can and added it to a new can? Yes. Have I just been lucky so far? Most Certainly. We ignore best practices at our own risk. We may ignore then and get lucky, but failure to have a catastrophe doesn't mean that what we did was wise or prudent. |
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October 18, 2017, 12:32 PM | #34 |
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Thanks Unclenick , I did not consider they can and would run tests on the stabilizers in the powder to determine if mixing it would be a good idea . This brings up the next logical question . How deteriorated would they let the powder get and still allow mixing ? I'd have to assume not much more then ( using the year analogy ) 5 years of deterioration would be max I'd think or 25% ????
Also , not sure if this was discussed but Assuming the powder is stored relatively consistently does powder generally deteriorate evenly or does it slowly deteriorate then one year it just starts falling off the cliff sort of speak ?
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If Jesus had a gun , he'd probably still be alive ! I almost always write my posts regardless of content in a jovial manor and intent . If that's not how you took it , please try again . Last edited by Metal god; October 18, 2017 at 03:19 PM. |
October 18, 2017, 08:15 PM | #35 |
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MG,
If they are doing a I suggested (and I haven't talked to any of them about it), I'm thinking they probably would project the expiration based on the lot's measured stabilizer deterioration rate history. With different balances of chemical species and each chemical having different lot impurities, they probably break down at different rates that you can attempt to project by trend line. Your second question is a key one. The bigger the powder mass, the greater the chance that not just the odd individual molecule, but several near one another somewhere in the mass will break down at the same time, creating a pocket without enough stabilizer to scavenge all the acid products, so the breakdown spreads out, staying ahead of the neutralizing activity. This starts the mass breakdown. It's why you can load a bunch of rounds and only find breakdown in a few, as I described before. The more stabilizer that is depleted, the greater the odds of this happening become.
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October 20, 2017, 09:39 PM | #36 |
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I've done it, but be aware if you do, this can happen.
http://www.ramshot.com/consumer-alert/recall-notice/
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October 21, 2017, 04:18 PM | #37 |
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I don't see a reason given for that recall. I wish they'd state the problem. My memory says that at one point there was a recall of powder because a similar looking but wrong type was in some packaging. I don't even recall what company it was at this point. Over time, things happen.
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October 24, 2017, 12:43 PM | #38 | |
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If a Corporation is given a choice of scrapping defective product and thereby losing profit, or selling it, to a buyer who does not know it is bad and can’t prove it is bad, what course of action do you think the Corporation will take? The answer is that the Corporation will ship the defective product and take the profit. Anyone remember the Volkswagen engineers, guys who were so environmentally righteous they grew wings? Do you think Volkswagen Management and all the Software, and Test Engineers did not know what they were doing when they wrote the software requirements, verified the software, verified the emissions system which only turned on when the car was in an emissions test? The future is hard to predict, but in the short run, Volkswagen made one heck of a lot of profits selling zippy, fuel efficient, highly polluting diesel cars. I am 100% certain that if defective powder lots made it on the market, it was because Corporate Management over ruled their written Quality Assurance requirements and shipped bad product, because, the company would make profit now, and the problems of sub standard gunpowder would not be revealed for years to come. By then it would be someone else’s problem. I am equally certain they did not start out meaning to make bad product, but given that defective product is what they produced, that is what they shipped. And that is what you bought.
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