Most of my issue with the 357 Blkhwk is at the forcing cone to 1" into the rifling. Also almost none down the barrel.
This could simply be the powder your using not getting along with that particular bullet. Unique is a GREAT powder don't get me wrong, and can be used to do a TON of loads with, it isn't however the overall best in all of them.
35, it leaded terribly with OT at 7.5 grs Unique, which I felt was a very high load.
Like I mentioned above, the powder can and does have an influence. It is how it burns or the pressure it produces that does it. While your charge of Unique, might be on the upper end for that powder, if you look at the pressures listed in the bok along side most of the data, you will see that maybe using something like HS-6, 2400, or AA-7 or 9 will give you higher velocity but slightly lower pressures.
You don't necessarily HAVE to load to the very top end, but one powder going say 1150fps, might lead the heck out of your barrel, another slightly slower or faster, loaded to the same FPS might do just fine. Like I mention it is a balancing act to match the load to the lead.
With OT bullets I ran them to the top loads in my GP-100's with 296, and they shot excellent. Doesn't mean they will in your revolver, but you have to play with it a bit to find out. I know right now isn't the BEST time to be trying out new powders or even finding them for that matter, but with a little patience they are there and can be found. Personally I would set the OT aside, and work on the other ones you have. Those cast from the wheel weight alloy should do much better with the Unique, but you might find they do their best at a lower end charge. Start low and work up. If your size is good and your lube is good, they should fall in line in short order.
One other thing, if you find that your bore is restricted where it is screwed into the frame, this can be corrected. Do a net search on fire lapping Ruger barrels, and it should bring you up plenty of good reading.