I'd start at max load, since milsurp 4831 will be a lot slower burning that modern canister 4831
That's a pretty broad statement. Military grade 4831 varied from lot to lot, just like powders made commercially today do. The only thing is, the lots made under wartime conditions had wider tolerances and that old powder could be found at both extremes of those tolerances.
I mentioned I had purchased a large amount over 50 years ago. There were three different lot numbers in that purchase. One of them was faster than IMR4831 and closer to IMR4350 in burn rate. The other two lots were very close. I kept a 50 pound keg from what I felt was the slowest of the three and it's very close to modern canister grade burn rates.
Even with max loads, in mid size cartridges it will be possible to reach slightly over max pressures but I seriously doubt any pressures that will have catastrophic results.
OP, your powder tins are likely just printed "4831" on a white label. Back in the day those were packaged, hand loading was considered to be "Alchemy" and only done by "Heretics" and everything was suspect and dangerous. Attention spans weren't any longer back then than they are today.
The thing is, there was some truth in those fables from the past. Some of the powders were no longer stable but sold anyway, Unstable powder has an acidic smell and is often rusty/dusty and the metal on the inside of the tins will be rusty. In severe cases, maybe even rusted through or if the powder is well on it's way to breaking down completely it will be seriously clumping, to the point you can't pour it out of the tins.
As mentioned, shoot it and sell the tins, if you can find a collector that wants them.
