Re: 231 vs Unique in 45acp
If you're loading large quantities on a progressive press, 231 is one of the best choices for consistent metering. It's my go-to powder for bulk loading 380 ACP, 9mm Para, 40 S&W, and 45 ACP.
I run 5.0 grains (5.3 is Hodgdon's book max) under a 230 grain bullet, whether cast, plated, or jacketed. Velocity is about 790-810 fps from my Kimber Custom depending on bullet type, and accuracy is fine for mass produced knockaround stuff. Some powders give better groups with cast slugs- Hodgdon Clays being the best I've tried so far- but since that powder doesn't meter as well through my Dillon, I stick with 231 for bulk loading.
I've also noted that, at least with my pistols, the bullet makes a bigger difference in accuracy than the powder type in most cases (powder charges being consistent of course). My best groups have been with my hand-cast bullets followed closely by Hornady XTPs. The best cheap bullets I ran across were IMI 230 FMJs.