Right now, my two favorite powders, W231 for pistol and Varget for .223 are both extremely difficult to find on the shelf right now.
I've been forced to experiment with powders I'm not as familiar with. For all the nay sayers about UNIQUE, it does well for me, esp. in .45ACP. It's generally less expensive, and more available these days as well. It also meters just fine in my Lee perfect powder measure as well as my Lee auto disk. But I still prefer W231 by far.
One thing about Unique, you can load it in just about anything. There are even recipes for light gallery loads in most rifle calibers. I've done this before with lead cast bullets in .32 winchester special without the need for gas checks because it keeps the velocity below 1400 fps.
Whatever you do, stay far away from IMR 700x. It's available and I see it on store shelves everywhere, but beware! That stuff won't meter reliably
AT ALL! I'm not talking a little bit here, but loads could be off as much as a grain or two.
This stuff clearly isn't for the beginner. I had some success using the lee powder dippers, but loads were still somewhat inconsistent even then, depending upon how it settled in the scoop. At least I only bought a lb. of it to experiment.