Year old powder slower?

[jmden]

Hi,

I've got a question regarding some interesting numbers off the chrono. Last year this time I had a load for my 300RUM doing just about 3400fps with a 180g Accubond over 96.3g Retumbo purchased 9/04. This year I had a few of those loads I put together last year still around and thought I should reconfirm my velocity. I've found it to average about 3285fps over about 10 rounds with about a 20fps spread.

I'm using the same chrono (Oehler 33P) at the range as last year. A local 1000yd. world champ Palma shooter uses this chrono and just checked his loads on it the other day. He's found the chrono to be consistent and accurate from year to year.

Any ideas to explain this?

Thank you!

 

[LB]

was your ambient temperature the same?

Powder stores well for decades, in the closed canister or as assembled cartridges.

 

[Buffalobob]

Do not know about it being slower. What I do with year old bullets is run them all thourgh the seater die to break them loose just in case they have become stuck to the neck. I don't know if it helps the bullets but it makes me feel better.

 

[jmden]

Oh, sorry. Forgot to mention that. I keep my rounds at refrigerator temp when I go the range in an attempt to more closely simulate hunting temperatures for the powder. Other than that, the ambient temps last year were hovering at 50 degrees F (after checking lasts years records for those rounds shot at 3400 over the chrono) and today the ambient temp while shooting was 66 degrees F. Since I've got the rounds in a cooler, I'm not sure how much difference the ambient temps make, but they weren't tremendously different anyway.