Old 4831 weighs less per volume

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I have a 25 year-old can of IMR4831 and weighed a measure of 41 grains. I took a new lot and the same volume weighed almost 47 grains. What gives?
 
This is not an unusual phenomenon at all. For one thing, volatile solvents in the powder do evaporate
over time, as does any moisture that may remain in it.
Additionally, modern powders tend to be somewhat denser that their early counterparts.
If you have a "shortcut" version, this is particularly noticeable.

Always work up from a safe level when you change even a powder lot, let alone something from 25 years ago.
Regards, Dave.
 
Makes me wonder if SPEER had an old batch of powder as in the 6th ed 1964 manual it suggests 51g of 4831 as a max charge for 6.5X55 and a 140g bullet. I have found a few other anomalies in that manual for various powders and calibers, loader beware.

Cheers
 
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Not sure IMR existed as a canister powder back then. Likely means 4831 WW2 surplus canister powder, which was still a Dupont powder, originally sold as 4350data powder. They didn't have to designate them til the IMR canisters came out with the new batch. Seems to me IMR came out around 1973, which was a new batch. Think it says Hodgdon bought H4831 from Dynamit-Nobel Scotland instead of Dupont after the surplus ran out. So, there are some variations in it. Was just reading where Alliant has changed vendors on RL22, was Bofors (?), now Lovex/Explosia apparently. For those who may say it's the same as MRP, it probably isn't anymore.
 
What I need to know is, if I load 41 grains of the old stuff, will it blow up in my face? I'm using a lighter load from a mid-80's manual.
 
I thought it WAS a safe level until I compared it to a new can of powder. Having established that powder likely gets lighter with time, will a minimum charge still be too much?
 
If 41 grains is the recommended starting load, then that is where you should go.
Whether the powder is old or new is irrelevant.
The newer powder will simply occupy less space, since it is heavier by volume.
The end result may well be different, of course. Dave.
 
Eagleye said:
If 41 grains is the recommended starting load, then that is where you should go.
Whether the powder is old or new is irrelevant.
The newer powder will simply occupy less space, since it is heavier by volume.
The end result may well be different, of course. Dave.
Click to expand...

Sage advice here OP and if you still are not comfortable don't use it at all.
 
I still have some 30 yr old H4831 and it produces the same velocity as my new lots of LC and SC in the 7 rem mag. I haven’t compared weight/volume because I only charge by weight
 
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