Unique weight/volume differs from published vmd

[edmonds]

I was wanting 3.6 to 4.0 gr unique for 32 H&R loads. I used Lee's auto-disk to throw 0.4 and 0.43 cc (4 times each) and measure weights with lab's analytical balance. I get 7.66 gr/cc versus Lee's VMD data, which gives 9.16 gr/cc. I don't have routine access to a scale, so I wanted to calibrate my throws and then use the auto-disk to meter powder by volume. But the difference (about 16%) is so much greater than the published values that I am worried about using my calibrated values. According to my measurements, I should use 0.5 cc unique instead of Lee's value of 0.4 cc.

Any comments/suggestions?

 

[RICHGCOOP]

I get about the same thing. Thy stay on the light side.
Would be nice if it was closer.

RICHGCOOP

 

[Rick Courtright]

Hi,

Any "volume to weight" chart is just a guide, whether it's Lee's VMD chart in the book, their slide rule tool w/ the dippers, the various bushings used by Lee, RCBS, and virtually all the shotshell loader mfrs, etc.

If you're using "fixed" measures, such as the dippers or bushings, you'll need to to a little experimenting to get as close to the desired charge as possible, w/o going over. Sometimes you can come pretty close, other times you'll fall short, perhaps shorter than you wish.

Enter "micrometer" type adjustments, such as the various manners in which powder measures, "universal" charge bars for shotshells, and others are adjusted. There you CAN get pretty much spot on w/ the charge weight you desire. Still takes some playing around.

So... best thing I've found is to make my own chart AFTER I've roughed things out using a spreadsheet calculation based on Lee's VMD chart. That way, my own figure will put me where I want, each time UNTIL I buy more powder. Then it's "start all over again." Each lot is slightly different, and I recall reading somewhere a tolerance figure of 10-11% being normal and acceptable.

Sorry... it's always gonna take some work, and may never put you exactly where you want to be short of hand weighing each charge!

Rick C

 

[Jimbo357mag]

I would say a scale is in order for anyone reloading ammo. You just absolutely need to check the powder charge going into the cases once in a while to be sure you don't blow something up. The Lee scale is inexpensive and works very well with small charges. It is very accurate, It can be a little awkward to use at first but once you learn how to set it up it will never let you down. I have a inexpensive digital also that I don't trust because of a wandering zero but it does work as a safety check when doing less than max loads.

http://www.midwayusa.com/product/712103

...Jimbo

 

[wwb]

As Jimbo said, buy a scale.... a Lee scale sure won't break the bank.

Another thing that should be mentioned here is that when you buy your next jug of powder, even though it's the same brand, the density is almost certain to be slightly different. I have seen as much as .3 grain change in an 18 grain load when loaded volumetrically (with a powder bushing). Not a big deal for little plinker loads, but if you start loading bigger stuff at max, it becomes VERY important.

 

[anachronism]

Trust nothing, verify everything. Buy a scale. You can often find used ones at gun shows for $25.00 or so. Scales are safety equipment, and really should be purchased first.

 

[edmonds]

Thanks for all the replies. I decided to get my own scale and periodically check (maybe every 5th) the charge by weight. I have only used TrailBoss, and I used volume measures after determining VMD of my bottle of powder with an analytical balance. You can't overcharge with TrailBoss. But I am going to more cautious with other powders, such as Unique.

 

[M'BOGO]

That seems to be the norm, as far as light charges from the Auto-Disk. Which isn't a bad thing, another good idea is a set of the check weights for your scale. I like the added piece of mind they give.

 

[Driftwood Johnson]

You can't overcharge with TrailBoss.

!?!?!?!?

Howdy

With all due respect, you are a relatively new reloader, are you not?

You most certainly can overcharge with Trailboss.

Due yourself a favor. Get the scale. Weigh samples of your charges. Nothing wrong with weighing every 5th when you start out, but you should start to see some patterns. After a while, you can cut back on how frequently you weigh your charges.

Also, ALWAYS do a sanity check for every loading session. No matter if you did not change anything from the last time, ALWAYS throw a few charges for nothing to make sure no gremlins snuck in while you were not looking and changed something.

And never assume you cannot stuff an overcharge into anything. Yes, Trailboss was developed specifically to put small charges of Smokeless in large capacity cases, but you can still stuff in an overcharge if you are not careful.