I have loaded 62 gr with the old surplus 4831, but get the same velocity, 3200 fps in 24" barrel, using 60 gr of the current stuff.
Ted
Ted, I found the opposite about the difference between old and new H4831.
We once bought a 50 pound keg of the old surplus, for about $20.
I seldom got more than 60 grains in the 270, because of having to tamp, then squash it pretty good, with a 130 grain bullet.
When the newly manufactured H4831 came out, Hodgdon stated you could use the same loading data as the old. I had access to a chronograph, so I loaded two batches of five rounds, exactly the same, only one batch had 60 grains of the old, the other, 60 of the new. I got just over 3000 with the new and over 3100 with the old. And, the old gave less difference between high and low.
I still have some of the old surplus and waiting 'till a factory delivers an RCBS chronograph. When it comes I will again check the old and the new, to see if there is any deterioration of the old powder. Some years ago I checked quite a few loads of the surplus and always got 3100 and change with 60 grains and 130, while 58 gave 150 grain about 2925, and little variance.