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  #1  
Old 08-17-2012, 04:08 PM
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Propellant Bulk Density


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I'm a wee bit flustered here. I've been handloading rifle and pistol cartridges for 18 or so years.

Just started using QuickLOAD, so to be thorough, I thought I'd check the bulk density of some of my propellants, esp. since the temperature at the range in the People's Republik of Southern Kalifornia is over 100 degrees F this week.

I have a bunch of surplus WC852F, which is comparable to H380 &/or BLC-2 (depending on the lot). Here is how I determined the density:

Get a sized, primed case. Put it on Dillon scale. Zero it.

Fill to the top with distilled water, trim the water level with a steel ruler so that the meniscus is perfect. Weigh it. Weight in grams equivalent to water volume in CCs.

Empty case of water. Blow out with compressed air. Blow in some brake cleaner (kiss that primer good bye!), blow it out again for 30 seconds or so. Let it sit a spell.

Put it back on Dillon scale. Zero it.

Take scale pan, fill half way with propellant. Put powder funnel atop case. Pour in propellant. Rap case sharply on side with metal object about 50 times. Remove funnel, let a tiny heap of propellant stay atop cartridge (easier than trying to cut it level with a steel ruler, and, it makes not much difference in any event.)

Weigh it.

Divide. Third grade stuff.

For the WC852F, I get <table border="0" cellpadding="0" cellspacing="0" width="175"><colgroup><col width="103"><col width="72"></colgroup><tbody><tr height="20"> <td class="xl65" style="height:15.0pt;width:77pt" height="20" width="103">0.0678</td> <td class="xl64" style="width:54pt" width="72">grams /cc</td> </tr></tbody></table>which, compared to a couple of identical references (0.0691), is about 2% heavy; no biggie.

Now, try the same thing with a lot of H4895 I've had for a while (not much longer than the WC852F, mind you!)

<table border="0" cellpadding="0" cellspacing="0" width="140"><colgroup><col width="68"><col width="72"></colgroup><tbody><tr height="20"> <td class="xl64" style="height:15.0pt;width:51pt" height="20" width="68">0.0634</td> <td class="xl65" style="border-left:none;width:54pt" width="72">grams /cc</td> </tr></tbody></table>compared to the same references (0.0728 gram/cc) this is about +15% heavy. Sheesh.

Repeat for a lot of Varget, same approx. age.
<table border="0" cellpadding="0" cellspacing="0" width="171"><colgroup><col width="99"><col width="72"></colgroup><tbody><tr height="20"> <td class="xl66" style="height:15.0pt;width:74pt" height="20" width="99">0.0632</td> <td class="xl67" style="border-left:none;width:54pt" width="72">grams /cc</td> </tr></tbody></table>compared to same references, (0.0731 grams/cc), about +15.5%

I did the same trick with AA2200DP, compared it to AA2230, it was right on the spot.

All of this propellant has been stored in the same place, in original 1 lb containers, in a Southern Kalifornia garage that gets a little warm sometimes, but the weather is generally not to hot or cold with moderate humidity. Besides, the bottles are all nearly full and sealed.

What the What is going on here? I have repeated the Hodgdon tests enough times to (hope I know that...) I am not totally nuts.

Some adult supervision, if you please?

mac
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  #2  
Old 08-17-2012, 04:26 PM
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Densities will change with the seasons, and age. They are constantly giving off, or taking in the atmosphere. If they didn't do that, when you opened the container you would smell nothing.
Also remember that powder is made in a production line. How many times have you had something in life that is perfect repeatedly? Powders are blended and re-blended many times. So your bottle of powder may well not be exactly the identical composition the whole way through.

The references are just that, references; NOT exacts. Also tamping the cases gives an artificial pack factor that will skew your results.

This is some other References that you may find helpful from Lee. You don't need to go into the production you did for the answer.
http://www.leeprecision.com/cgi-data/instruct/VMD.pdf

VMD explanation - Support Center
This one will show you the quicker way, FOR YOUR powder specifically.

Last edited by Darkker; 08-18-2012 at 08:09 AM.
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  #3  
Old 08-19-2012, 01:52 PM
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Exclamation Duh, and, maybe.

Thank you for your reply.

I was using tables identical to the Lee one you referenced above compare my results.

All four of the powders tested thus far are approximately the same age (as far as my stewardship of it goes) and stored in the same place for about ten years in gasket sealed propellant containers. Although, the WC852F was a pull down MIL powder, so who really knows how old it actually is. It was one with a close to nominal bulk density (BD).

I realized that rapping the case will change the measurement; I made the (possibly) erroneous assumption that would be the way to do it. I didn't push the stuff in, I left gravity settle it by whacking the side of the case. 14% error or so seems a bit extreme, but the error is in the right direction -- more dense than nominal.

That being said, it is interesting that the first two propellants I did were ball powders & fairly close to the nominal BD (same procedure), while the last two were tubular powders, with the results between the two types vastly different. Duh. I was a little too confounded at the time to consider that. I'll re-try and report back soon.

However, I disagree with your suggestion that this investigation is not necessary. People who have been using QuickLOAD (QL) for a long time point out that if you really want accurate results from the program that it is important to check &/or adjust the bulk density for individual lots of powder.

In fact, working backwards through some previously loaded and chronographed loads (I keep pretty good records), QL didn't get close to the instrumental muzzle velocity until I adjusted the powder density -- a couple percent made a significant difference in the QL data. Voila! Pretty close after that even w/o adjustment from instrumental to muzzle velocity (not taking into consideration the velocity lost between the muzzle and the middle of my sky screens.)

I am going through all this trouble to try to hit a muzzle "sweet spot" condition for the bullet to leave the bore at a time of maximum constriction from the blast; some fairly rigorous investigations by Chris Long et. al. have shown this approach to have merit. In the past I have burned thousands of dollars in components finding those sweet spots by trial and error -- I am just trying to get a little smarter about it. Long makes some pretty good arguments.

See Optimal Barrel Time Paper for any who are interested.

mac
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  #4  
Old 08-22-2012, 04:27 PM
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Nope, it's even _less_ dense!

Well, I checked the Varget and H4898 bulk densities (BD) again, this time w/o tapping the case. I realize that my previous observation "...but the error is in the right direction.." was mistaken; clearly I am getting a BD of LESS than what is considered standard.

I retested w/o tapping the cases today and, of course, got even smaller numbers:

H4895
  • 0.0691 grams/cc vs. 0.0728 grams/cc considered standard (-14.8%)
Varget
  • 0.0628 grams/cc vs. 0.0731 grams/cc (-14.1%)
Scale calibration was verified. Measured case capacity of 67.8 cc water is in a reasonable range. I have to look at some more propellants later tonight.


mac
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  #5  
Old 08-22-2012, 05:20 PM
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Well, I gotta be honest, I got somewhat lost here
So this may not be pertinent to your cause.
The BD will change with age, as the solvents gass-off, dry-off. As long as it is proportionate to the burning rate.

Another possible issue is that Hodgy doesn't(that I've ever seen) List any standards for either burning rate, BD; so what is outside of "normal"? Also they did a pile of supplier switching several years ago, I wonder(based on personal experience with 2 of their powders) how that affected things as well. At the time, I found some HORRIBLE lot variations, FWIW.

Honestly don't know about QL, as far as updates etc. But if there are changes going on with the powder, you may well not jive with QL.
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  #6  
Old 08-23-2012, 01:37 PM
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Question Hodgdon Claims Propellant Characteristics Unchanged

I just spoke to a very disagreeable chap named Mike at Hodgdon. They don't release physical data about their propellants to anybody (that's understandable), and claims that, for example, the bulk densities I have been finding for H4895 in all manner of references, including QuickLOAD, of 0.0728grams /cc are "nowhere near correct."

It was painfully clear that he really was not interested in even hearing my questions (I din't get to ask very many due to continuing interruption), so I told him so and politely bid him good-bye.

The only useful information I got from him is that (paraphrasing), "...you could store that propellant for 40 years as you did and find no change in it; you can't get that kind of change without _doing things_ to change it."

So much for this quest. Thanks for your inputs.
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  #7  
Old 08-24-2012, 07:17 AM
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MZ5 MZ5 is offline
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I, too, have found Mike at Hodgdon to be an excessively disagreeable person with whom I have had the misfortune to speak on more than one occasion. Interestingly enough, I believe he is the one who told me some time back that my still-sealed container of H-450 was not suitable or safe to load, since it was a surplus powder that had not been manufactured for decades, that H-450 had always and only ever been a surplus powder, and there was no way to know what its properties might be now. This was odd, since the labeling on the bottle clearly stated it to have been new-manufacture (as opposed to surplus). But I digress...

I know that Hartmut (QuickLOAD code-writer/developer) has had or continues to have extreme difficulty obtaining information about powders from some of the suppliers. Prior to your post, I had reason to believe that Hodgdon wouldn't tell him anything at all. Your post supports my belief. Thus, as I understand it, Hodgy-supplied powders are tested by Hartmut in a calorimetric bomb to get data for the program. This leaves the data in that program somewhat open to variation in terms of what it predicts for Hodgy-supplied powders vs. what Hartmut has been able to measure directly from the lots he has/had.
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