with the powders I use, velocities and accuracy between lots is virtually non-existent. . . . especially with the magnums.
Given your namesake, that would make sense. At least in my experience (I don't load 460 XVR), when you're loading up magnums with magnum-slow powders (W296 etc.), there's little difference from lot to lot.
With faster stuff, I have noticed lot to lot differences. Once I got ahold of some Unique that was
spunky! Big difference in behavior compared to the previous # that I had. It had to be more than the 3% canister grade spec. Or so it seemed. Anyway, I adjusted my loadings and it made fine ammo. As a side note, it was during the shortage of '13, so maybe production was hurried, or something. Just a guess.
Moreover, I've noticed differences in density. This is likely due to the propellant drying out over time/use. On multiple occasions, when I got to the end of a cannister of powder and started a new one, I left my hopper setting the same, then weighed the difference. The new is almost always more dense than the old. I've done this experiment with Bullseye, W231, Unique, AA5, HS-6, Power Pistol, and probably others. Knowing this, if I do a work up with a new # of powder, I note it in my loading log. If it's a hot load, that recipe may be a bit too hot by the time that canister is near empty two or three years down the road when the powder is less dense.