Cleanest burning powder of choice for .38 Special, .45 Colt standard pressure and .45 ACP up to full hardball, but not +P is WST.
This was Olin's replacement for 452AA, which we used in competition for many years. Meters like water in the Star.
TiteGroup also very good in any application where you would use Bullseye, including rifle "cat sneeze" loads, but burns much cleaner.
For applications where you would normally use Unique in full-charge loads, such as .38 Special +P, .45 ACP and 9mm hardball level, 7.62x25 Tok, .30 M1 Carbine Olin AutoComp works very well.