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Discussion Starter · #1 ·
Hi,
I have read here & in various reloading manuals that when you change from using one lot number of a powder to another you should back off your loads & redevelope them. This is ascribed to the lot to lot variation in powders.
Now I'm not in any way a powder manufacturing guru, but isn't there a way the manufacturers could utilize test data they already have to warn us of trends?
Reason I ask is last year I got the intresting SomChem reloading manual out of South Africa, (Rheinmetall, Denel Muniton) and on their web site (SOMCHEM | Reload with the best) they list the velocity variations as a % relative to the reference lot for each type of powder. If you search for a load for a specific cartridge you can click on the powder number on the results page to get to the powder page. At the bottom of that page you can click to veiw the lot history.

Now I'm not saying this is perfect but it is better than what I have seen from other manufacturers! It does seem to me that pressure is more important, but for most reloaders a lot harder to measure.
Dies anyone else think this type data would be useful/relevant?
 

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I would think it would save me some testing, if it was found that the information was valid. A similar chart of variations resulting from temperature changes would be nice too.
 

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The Hog Whisperer (Administrator)
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They could.... but mostly, they don't
 

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Discussion Starter · #4 ·
Yup. Think that was my point. Do reloaders have enough clout w/powder companies to get them to make info availible, or are we just bottom feeders, not worthy?
 

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Discussion Starter · #5 ·
Ok, maybe I didn't say that well.
It is my understanding that the folks who make/blend/sell canister grade powders to the reloading clan go to some degree of testing to insure that the various lots are to some degree similar to what we bought last time. If for no other reason than to keep us from blowing ourselves up & suing them out if business.

Can we as a group, there are several what seem like highly qualified people here, can we choose some parameter that will be useful to us? Then can we as a group go to say SAAMI & get buy-in that this is useful & beneficial to all? It isn't like the powder companies can't sell all they make. In fact, data like this would make us all safer & maybe attract even more new folks.
 

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That would simply not work. Powder manufacturers test their powder lots much differently than just loading up some cartridges and shooting them. The differences they see would not universally transfer to load data. The same powder will behave differently in different cartridges and pressures anyway, there is no way to predict every slight difference. Heck, enough reloaders have trouble following the current published data anyway, imagine if they had to use math to ”adjust” their loads! The only way to insure safe data would be to provide complete load data for every new lot of powder. Ain’t gonna happen.




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The Hog Whisperer (Administrator)
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The people that sell the powder, are rarely the ones that actually make it. So..... might be difficult to get SAAMI to be able to do anything about it.
 
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The Shadow (Moderator)
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Here's the thing, you need to use words carefully in this conversation; and don't interchange them for others. This is how the powder business works in the US.

Manufacturers - Defense Contractors. Except for one private facility, they all use G arsenals. Of which most are superfund sites, and not exactly cutting edge. The one private facility is geared up to literally make 120 rail cars of powder, in a single lot run. Extremely large scale production, on extremely quick timelines.

Customers - Governments, military allies within NATO, and massive ammo producers(like Hornady). They buy said trainloads of powder, which in fact is built to, a set of specs.

Waste market - This is where junk goes. People go to auctions and bid on random lots of various things. Taking chances on all of the following:
What is burning rate actually is. Who the customer was, and what they actually spec'd, how far off of the original order it is, how old it is, why it is being thrown in the trash.


See every single lot of powder that is produced, is tested to be what is supposed to be. But that's literally a trainload sized single lot. There will be some variance on all sides of the spectrum that don't fit the spec, and get tossed or blended into something else. So when a junk trader comes in and buys random pieces of garbage, blends and slaps a label on a bottle; they don't know what it is supposed to originally be.

I used to talk with Dave before he left GD. When you buy WC846, that doesn't tell you shyte; other than the starting point for an order. The rest of the lot number from GD explains what the customer wanted. And Darkker who bought 100# on the auction house isn't the customer. So the answer and the powder manufacturers says is "kindly go outside and kick rocks".

All to circle back to say, yes things are tested on all sides of the ultimate usage. But where you lie in that food chain, matters a lot.
Does no one else remember the huge trouble that happened when Hodgdon changed extruded suppliers to Thales? The differences in the same branded names, was huge. No name change, no large campaign to inform of the formula change....
Lot variances can be all but non-existent, and add I've shared with pressure data; can be disturbingly large.

Cheers
 
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Well, I suspect we are bottom feeders. But realistically you have to consider that here in the US we live in a very litigious society so oftentimes common sense and technical correctness give way to legal correctness.

In the past, information has been published and computers proposed to simplify and/or assist loaders/reloaders in determining loads. They all require multiple inputs that must be utilized by the reloader and must be provided and maintained by the manufacturers. For instance, if you go to the SoMChem site you will see numerous velocity deviation corrections to the data listed on the containers. In some cases errors on the order of 2%.

Ultimately, the more specific the data provided the less likely the product will be used for unintended purposes or application. After all, we are dealing with a explosive.
 

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I've never worried about different lot's. Seems I'd buy a can of powder and next one the lot number was always different. Bought two can's one time and two different lot numbers. Never been a problem with me. I can assure you that if different lot number's bother you, simply rework the load. It'll make you feel better and the powder company's will appreciate the business.
 

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What Somchem's site offers is the result of firing a standard cartridge in a pressure and velocity test barrel with a standard bullet and primer and COL they've chosen as a reference. Then they report how different the new lot's resulting velocity is from that produced by the reference lot. What I don't know, though, is if that velocity is for the same charge weight as was used before or for the same maximum load pressure as was achieved before. I also don't know exactly how it will carry over to other cartridges or bullet weights, etc. I assume the number is for the same charge weight, which is how relative burn rate tables are created. But that means producing higher velocity is presenting a faster relative burn rate and it is producing higher pressure. For a maximum load, that could cause issues (battered brass, pierced primers, sticky bolt lift, etc.) If it is for the same pressure, then the number is telling you what energy you can get out of a particular lot of powder, but then you'll still have to work up to the percent difference in velocity. But I don't know which it is.

Since you have to shoot to check for pressure signs anyway, you may as well stick your chronograph out there and see how velocity compares to what you are accustomed to getting from that powder, starting from the bottom listed load and working up. If you have a Pressure Trace, use that to tell you when you've hit your old pressure. But if I'm having to do all that anyway, I'm not really sure how much value the published data has to me. I'd want to know their method, first.

I tried asking Hodgdon for the various QuickLOAD parameters years ago and was told it would cost them $50,000 a lot to have a lab make all those determinations, so they don't. Their old print manuals claimed they kept burn rates to ±3% for the powders they distribute except for IMR which, at the time, they said was ±5%. Valleyfield has changed the processes since then, so I don't know a current number. QuickLOAD's author deduces powder characteristics from closed vivacity bomb tests and doesn't rely on the powder companies for data. I also think there is some hesitancy about revealing what Hodgdon considers proprietary knowledge, where some of the foreign makers are much more forthcoming with their information.
 
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My understanding is that Hodgdon is the only company that won't give QuickLOAD's developer ANY information. He had or has to bomb-test everything from them. Perhaps that is (no longer?) the case.
 

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The Shadow (Moderator)
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GD and seemingly Thales, doesn't seem to want to play well with him either. At least in certain instances.
 

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My understanding is that Hodgdon is the only company that won't give QuickLOAD's developer ANY information. He had or has to bomb-test everything from them. Perhaps that is (no longer?) the case.
I think he does his vivacity bomb test on everything. If you look at his numbers, they don't exactly match numbers published by VV or Somchem, so you can figure he was testing a purchased lot. I believe the deduction of powder properties from the result of that test was one of his original developments back in the late '60s. It's also built into QuickLOAD, and if you have ten of those time-step pressures from a vivacity bomb data recorder, you can put them in yourself and get the results. I wonder how many of his customers have done that?o_O
 

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He has (had?) carte-blanche from at least one of the major european manufacturers, but I understand like you; that he did bomb testing anyway (at least on some). I kinda-sorta wonder whether testing now is reserved for new or previously untested powders at this point.

All I know is that it's the Hodgy-supplied stuff that's sometimes WAAAAYYY off. Almost-dangerously far off, IMO. That could be due to a number of factors, but at least some of the key ones relate to no data other than from the bomb test.
 

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Discussion Starter · #16 ·
All I know is that it's the Hodgy-supplied stuff that's sometimes WAAAAYYY off. Almost-dangerously far off, IMO. That could be due to a number of factors, but at least some of the key ones relate to no data other than from the bomb test.
Darker, just to clarify, are you saying the Quickload results are WAY off, or are you saying the powders vary so much they are dangerous if you substitute a different lot of the "same" name powder in a previously worked up load in a real gun? If it is the latter, that is VERY scary!

I hate it when the BOOM goes the wrong direction!
 

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I'm not Darkker, but since you quoted my post, I'll answer. (-:

Sometimes QL's predictions are WAY off. The worst I've experienced has consistently been from Hodgy-supplied powders (GD's powders, specifically). The reasons for that can include each of the things you mentioned, and others as well.
 

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Hodgdon imported some Varget in the past ('90s) that was so far off that a lot of shooters complained about it. I believe it was part of the impetus for their QC system upgrade around 2000. Since then, Valleyfield's manufacturing processes have changed and I don't know how close to current data the old powders are. Unfortunately, I didn't keep records of enough of the old Hodgy load data to be able to spot if they retested and changed anything. The expectation would be they would want to keep the old load data as valid as they can for safety reasons.

If you want, you can compare QuickLOAD results the Gordon's Reloading Tool results. GRT uses Pressure Trace and other data from handloaders to try to improve their powder files, so I find it worth looking at both sometimes. The GRT interior ballistics software uses a somewhat different model than QL does.

Read through the interior ballistics modeling formulas discussed in the Ballistics forum for what can be even more accurate predictions of velocity.
 

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Those relatively small variation's in velocity are assumed to be from different burn rates. But couldn't it also be from different weight's in the bullet's themselves or maybe from small differences in capacities in the case's used? Who knows, Maybe it's a difference in the primer's!
 
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