That is where it can get complicated, notice in loading manuals that bullet weight change can cause need for different powder to maintain best accuracy. All of my guns have a tuned load for one weight bullet and I use one powder for this reason. I know what you mean about collecting different powdersdo you change powder for different grain bullets
Thanks for the info. I'm on this site so much, trying learn as much as I can. Sometimes it prompts me to as questions, sometimes to validate what I'm thinking. I want to learn as much as I can, for what I'm loading now and for what I want to do in the future. Currently I'm loading .280 , 7mm08, .204, and .350 legend. I keep a journal of what I'm loading for each round. I research and ask questions before I make any decisions or changes.I suppose the best answer then is to open your reloading manual for the cartridge you are interested in and pick the powder that shows up under the most different bullet weights. Will it be the most accurate? Maybe, but if so, it'll likely only be for a particular bullet weight. Will it provide the highest, SAFE velocity? Maybe, but only for one particular bullet weight. And that could be okay! It depends on what matters most to you.
But since you have a variety of cartridges you load for, there will be 'powder overlap' and that will be a good thing. A powder for your 7mm-08 shooting light bullets might be great for your .257 Roberts shooting heavier bullets. Something along those lines. So you will probably still need a few different powders, but they'll be able to work in more than one cartridge, which is handy.
But a blanket statement, "Can one powder work for all bullet weights in a particular cartridge?" would make me want to say "NO". Think of a .30-06 which can handle a 100 grain bullet on the light end and a 250 grain bullet at the heavy end. No one powder is going to accommodate that range of weight. But to be fair, no twist rate is going to work with that range of weight either.
Good luck in your pursuit. The 7mm-08 is a great cartridge. Very versatile and effective for a lot of different hunting situations. Varget is a great 'all-around' powder for it. Hodgdon shows load data for bullet weights from 100 grains up to 175 grains. (See attached)
I love the 260 round, but I can't find in platform I like. Remington made it one year in the 5r gen ll, then stopped before I had the money for it. I think I like rl17 . What I don't know is what is the difference between rl16 rl17,or rl26.I chase velocity . if a different bullet will produce more velocity by using a different powder , I'll give this other powder a try . I worked with a 260 rem last summer . with 120 grain bullets I used RL17 , with 140 grain bullets I used RL26 .