No it shouldn't be attempted with any random powder, but there are at least a few safe options.
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Some loads are listed as minimums because that's just what the people doing the testing started with. Other loads are the minimum because any less could be dangerous.
These answered it, confirmed my suspicions as well. I'm at that confident and curious point, so I'd rather seek out the "Wisdom of Experience" rather than the "Wounds of Experimenting".
RE: Reloading/Safety - I appreciate the concern, though I am actually well-read on reloading. I have read ABC's, Speer, Hornady, even P. Sharpe's 1937 edition (which is QUITE the read, btw.), as well as reading the actual SAAMI Pressure and cartridge diagrams for my caliber(s) of choice (detailing chamber specs AND cartridge specs), AND the the Documentation on how SAAMI gauges the pressures and establishes cartridge pressure limits.
However, there are questions that rise that only EXPERIENCE can answer. My question, for instance, is viable - given consistent burning powders that have a consistent pressure wave, and thus predictable behaviors at lower charge amounts. However, since I do NOT know the behaviors of all powders, nor do I want to "experiment" to find out, I seek some advice of more experienced reloaders.
Where my question originated was with a discussion on cartridge versatility with a friend - and the short story is using a .308 cartridge components in a .30-06 case. In the strange and random event that you cannot find .30-06 in stock, but .308 is available, you may need to "salvage" a few rounds. I know this would seem far fetched - but the recent ammo shortage is teaching us all a few things...or, alternately if you're at a remote location that just ran out of .30-06 but had .308, this could be an idea.
Given that the .30-06 has more room to work with in the case, you could THEORETICALLY break down a .308 case, throw that charge into a .30-06 (given similar charge amounts using shared powders in the manuals), and it should line up to a "safe mid-range" for a .30-06, provided you use ONLY that bullet you pulled from the .308 in the .30-06. Of course, this assumes that you travel with an inertial bullet-puller and a Lee-Loader.
My concern came with the idea that the .308 you are pulling from has either a smaller charge than usual (Federal ammo occasinally runs "cool"), or you have a "reduced recoil" round. ALSO - factory ammo CAN use Proprietary powder - which is tuned to THAT cartridge specifically, and MAY do odd things if given more "running room". However, if both .30-06 and .308 are using the same powders in reloading manuals, chances are that their Factory powders are also close enough in behavior to not pose a large problem - though this is pure speculation. ALSO - I'd ONLY consider this with THESE TWO cartridges specifically.
