Genesis you sound in the same boat I am. Can NOT find any, and I mean ANY powder locally. I was lucky enough to come across an older reloader that was closing up his gun shop for retirement. He sold me a keg of Win 540 (HS6) and a keg of of Win 570 (HS7).
I did some research and the common thread was many said HS6 often prefers magnum primers (not always) and mid range loads and up for best accuracy / clean burn.
A real clean burn isn't important to me since in my desperation I tried black powder. Wow, what a mess. Didn't help that I didn't know what the neck I was doing and made everything messier than it needed to be. I was so surprised that Hoppes #9 had little to no affect on it lol.
As for load data there is tons for HS6, not so much with the HS7. I loaded up some HS6 in 45 Colt (best round ever invented), some in 38 Special, and some in 357 mag. Unfortunately haven't had a chance to test them lately so no personal experience yet. Not really sure what to do with the keg of HS7. If anyone has any loads for that in 357 or 45 Colt feel free to shoot me a pm. Or if you live in CA and you want it I could make you a good deal on it.
Genesis be sure to let us all know how you like it. Oh just fyi, Jon Linebaugh's pet load for general carry when not in Grizzly country is 13gr of HS6 under a 260gr Kieth type semi wadcutter. He says it's good for about 950 fps in his S&W model 25 with a 4in barrel. My Speer Manuel #12 lists 12gr max for stardard pressure loads that they got 945 fps from their test barrel. The manual says they used a 6in S&W model 25. So Jon's 13gr load may be slightly +P. Just keep that in mind if you have an 1873 Colt or levergun that could accidentally injest that load.