HS-6 [aka Winchester 540] is one of Hodgdon's imported powders. It's one of the pistol powders that seems to be easy to find right now. You may be out of powder and find nothing else in your local store, which is what happened to me. It was a choice between 8 pounds of 700X or 1 pound of HS-6. I've never used either, but it took all of 3 Milli-seconds to decide not to experiment with a $140 can of powder.... which is how the HS-6 followed me home.
Upon opening the can the first thing you'll think is that someone tapped your 3/4 full can !! This is a VERY dense powder. Second thing you'll think is "this stuff looks like Unique"; its all rough, coarse, black crystals exactly like Unique. Last surprise is the load-to-case fill. You read that a load is going to be in the 6gr range and expect spillage, but then you see it only half fill the tiny 9x19 case.
Based on a quick work-up in the backyard, I loaded RMR 124gr RN at 1.130" with 6.2gr. I found this load safe in my SP-01, but probably way over PF (~1100 fps ??). I would not go that high next time for target loads, because it had no problem operating my slide with the stock 18# spring. However even at this higher load, HS-6 was still somewhat sooty. The receiver was totally clear of unburned trash, but still it made me think this might be a better match for something that could digest higher pressure loads.
On the up side, it metered well, and the accuracy was splendid. I took 100 rounds each of VV N330, IMR 7625 with 2 different 124gr bullets, and the RMR 124gr to a lunchtime fun shoot today. In unsupported plinking, shooting 10 of this, then 10 of that... HS-6 out-shot them all.
Bottom line: I don't think HS-6 is going to displace any of my favorite powders, but if you need powder don't be afraid to buy a pound. It's a workable 9mm and 40 powder. I'd certainly pick HS-6 over large-flake powders like Blue Dot or 800X.
Hope this helps!
