Have to agree with Longtom here! I've used HS-6 for about 20 years as well. Glad to see there is someone else out there that discovered it. It's always worked well in my 45 Colt loads. I originally started with 14 grains under a 250 or 255 cast bullet but have lowered to 13.5g in the past 5 or so years. Most recently I've tinkered with and changed to 19.5 grains of 2400. I don't know what velocities I'm getting out of my 7.5" Blackhawk for either powder but these are some stout loads yet from what I have read, they don't go over or near the pressure limits of the Blackhawk or Win 94 or other comparible leverguns.
(WARNING!!!! Definitely NOT loads for standard Colt or reproduction firearms!!!) Literature that I've read says it's about 1150 fps for both charges in a revolver. Recently I compared both loads (HS-6 and 2400) at 25 yards and found the HS-6 to be a bit more accurate. Shot 5-shot groups with ease under 2 inches with the HS-6. I too use both of these loads in my Win 94, my CR-45 H&R Classic Carbine and my Super Redhawk. With the 2400 load, I have shot some 5-shot groups of about 1 inch at 25 yards from the SRH. My Winchester 94, however, did have some parts break a few times (extractor, two ejectors, and a loading gate). Don't know if it's from these loads or just normal wear.
I've used 10.2 or so grains of Unique in the past but found the HS-6 and 2400 to be much more consistent with results on paper when loading heavier loads. Also, H-6 and 2400 meter much better when charging cartridges than does the Unique powder.
I used Unique for years in my 45 colt loads, (both lead and jacketed) but have switched many years ago to HS6.
I get better performance and it burns a lot cleaner.
My load is 12.5gr behind a 250-255gr bullet with a standard Winchester pistol primer and out of my 5.5" custom Blackhawk it runs right at 1040fps.
This load has been used in many Blackhawks and 2 Redhawks and 3 Winchester 94 levers including a 16" trapper.
So far we have not found a gun that didn't like this load.
This load is 2 gr under the listed starting load in the Hodgdon manual # 26 under IHMSA Handgun Silhouette loads for 45 colt on pg 584.
Give it a try.
I think your gun will like it.
LONGTOM