My new powder is heavier!!


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Fatelvis
April 4, 2010, 10:46 PM
I just used the last of an 5lb jug of RL15 for my competition AR loads. The powder measure on my Dillon 550 was set at 24.0 for the whole 5 lbs., and was wonderfully accurate with 77SMKs. The load was warm, but never had pressure issues or blown primers. Now, after using the old powder up, the new powder weighs 24.3grns, using the same setting. Should I leave it alone, or dial the measure down, so it weighs 24.0 again? Thanks-

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EddieNFL
April 4, 2010, 10:50 PM
Read what Zediker had to say about weight versus volume.

Sport45
April 4, 2010, 10:52 PM
You say these are competition loads? I recommend starting this new batch of powder at the published "start" load and working up to the best accuracy. Might not be the same as the old batch.

R.W.Dale
April 4, 2010, 10:58 PM
On a well known load of a set volume as with a measure I go by volume and not weight. WHICH I've noticed can vary from day to day depending on atmospheric conditions.

Fatelvis
April 4, 2010, 11:15 PM
Read what Zediker had to say about weight versus volume.
Eddie, I read a few of his articles, and I respect his knowledge of reloading alot, but could not find the weight vs. volume reference. Could you post a link?

medalguy
April 4, 2010, 11:16 PM
I just checked a can of powder, and my new 1 pound can weighs the same as the old one, 1 pound. :neener:

Seriously, the weight in my Dillon powder measure will vary by .1 or .2 gram or more from week to week depending on humidity. I don't change the measure but go with the same volume. I reload both in New Mexico and in Houston, set the measure in New Mexico with about 12% humidity and when I'm in Houston it may be heavier but I have always attributed that to the additional moisture content. Volume stays the same.

Yep, should read "grain" above. My bad. Just another good reason to NEVER use load data you find on the internet without cross checking it with at least two loading manuals!

steve4102
April 4, 2010, 11:49 PM
Any time you change a component or a new lot # one should back down and work back up.

Doug b
April 5, 2010, 12:04 AM
Yep your old load was right at red line.Start over and work up.

Roccobro
April 5, 2010, 05:42 AM
my Dillon powder measure will vary by .1 or .2 gram

You mean grain right?

Justin

ArchAngelCD
April 5, 2010, 06:33 AM
As I'm sure you already know when you are at the top of the charge range and you change powder Lot numbers you have to work up your load all over again. I know you were hoping we would give you a pass on this but you should have known better than that!! :p

SlamFire1
April 5, 2010, 10:16 AM
Dial it down to 24.0 grains.

Powder manufacturers mix stocks to get consistant burn rate by weight.

Fatelvis
April 5, 2010, 11:05 AM
I know it sounds bad, but I don't really have much time before the season starts, and working a load up from the bottom isn't an option. I'm going to dial it down to 24.0, as Slamfire suggested. I'll keep a close eye on the primers and primer pockets for pressure signs on the first fired rounds. If pressure seems to be an issue, I'll back off the charge another .2grns or more. I can't see two fairly recent lots of powder being that far off from each other.

ants
April 5, 2010, 05:11 PM
Some older manuals discussed the differences among the density of powder from lot to lot:

In their loading data books, Winchester states than acceptable tolerance is plus or minus 0.025 grams per cubic centimeter. If we work out the arithmetic for a 50 grain charge of Winchester 748 powder, we find that the grain weight of the charge could vary by 1.3 grains over or under.

This particular quote is from the Lee manual. Others make similar statements, without the math. One would be well advised to check and adjust volume-type powder measures as necessary when opening a new container of powder, since the values in powder manufacturers' manuals are given in weight, not volume. To be safe and accurate, you want to adjust by weight.

Sport45
April 5, 2010, 11:04 PM
If pressure seems to be an issue, I'll back off the charge another .2grns or more.

It's your rifle and your face behind it so you're obviously free to do what you want. but it seems backwards to me to do your pressure testing by starting at the high charge. Why not back off a little bit from max and see if the group size is acceptable before moving up? Were the 23 gr loads you tested in your original workup that bad?

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