You're certainly not wrong for trying or going that route but I doubt you'll get much data from others about it
just because varget works extremely well with a 308 doesn't mean I'm gonna put it in an ultra mag. It can be done but are there better powder choices? Yes.
on the flip side it's rare for 260 users to use 4831 as a 260 powder but it's certainly not wrong and it does work. Just not as ideally as others. (By ideal were talking about velocity to case fill, NOT accuracy/consistency of shots)
4831 is what I'd consider the fast side for 300wm (better for short barrel 300's) and it's also just a tad bit slow for 260 (can't seem to get enough to achieve high velocities).
If youre gonna have to choose 1 powder I'd stay with 4831 as the go between the two. Reloader 19 would also be a contender.
But I'd only do that if it's really important for you to have one type of powder... it's just best to get the correct powder(s) for the caliber.
260 rem
reloader 16
H4350
IMR 4350
imr 4451
*4831 (IMR and H): best for a minimum 26" barrel
300wm
IMR 4831* best for short barrel 300's but works with long too
H4831/SC* best for short barrel 300's but works with long too
Imr 7828SSC
H1000* best if you have at least 26" , preferably 28"
just some suggestions