Never used US869 in a STW but I use it a lot in 30-338 Lap Imp and 338 Lap Imp. My experience with it has been very positive but one of the things I found with using it, at least for me, was it needs the bullets to be seated out very close to touching because whenever I've backed them off and jump them further, the ES numbers will have huge swings. I pretty much only shoot Berger bullets so finding an accurate load with the bullets very close to the lands isn't a problem.
If you can't reach the lands with the bullet you intend to use with US869, it may not be a very good powder choice for you and could possibly give you some extreme ES numbers.
