26 has been the easiest of the group to find for me, but I don't see it as particularly similar, even though it is right next door on the charts. H1000, in big cartridges, seems to end up right around 100% fill, whereas 26 ends up around 90%, sometimes below. Not really sure why this is, but for those of us who live in frigid winters, you don't want to go too low on fill ratio and run into ignition problems.
TBH, doesn't seem like an issue with win mag, so disregard.