Unique has a largely undeserved reputation as "flaming dirt".
That's an artifact of using it in light loads and it's not the best choice for standard pressure loads in the .38 Special.
Unique is however my favorite powder in short barreled .357s. I wouldn't call it a powder for just "mid range" loads either.
For example, with 9.0 grains of Unique under a Hornady 125 gr hollow point (still .4 gr under max in the Hornady second edition manual) it generates an average velocity of 1,296 fps in my 3" .357 Magnums.
I prefer 8.5 grains of Unique as the cases drop out of the chambers without sticking, yet it will still generate an average of 1,243 fps with a 125 gr XTP in a 3" barrel.
That compares to a velocity of only 1,148 fps in a 3" barrel with a near maximum load of 20.0 grains of Win 296 (20.4 gr maximum, per the Hornady sixth edition.)
Unique is also a decent powder in .38 +P loads, along with Titegroup.
However, my favorite for a .38 +P load with a 125 gr XTP is IMR 800X. 7.5 grains gives me an average of 929 fps in a 1 7/8" Model 36, 951 fps in a 2 1/8 Model 60, and 1,030 fps in a 3" Model 13 or 3" SP101 - and the SDs are normally between 10 and 20 fps - superb consistency for a short barrel.
----
For .38 Special cast bullet target loads with a 158 gr LSWC, I'll use 3.2 grains of Red Dot. I've varied the charge up and down a bit over the years but I've found 3.2 gr gives me what I want in my various .38s and .357s. The load data is interesting as it has a range from 2.6 gr min to 3.9 gr max in the Hornady 3rd edition, but 3.5 gr to 5.6 gr in the 2nd edition - and the 2nd edition data in general is a bit hotter in general.
3.2 gr of Red Dot will produce 670 fps in a 1 7/8" Model 36, and 675 fps in a 2 1/8" Model 60 (I suspect the longer chamber loses as much velocity as is gained in the extra 1/4" of barrel). In a 3" Model 60 or Model 13, a 4" Model 10, and a 6" Model 19 it will produce 727 fps, 748 fps, and 794 fps respectively with SDs in velocity between 10 and 15 fps, which is again very consistent.
