I've avoided W231/HP38 because it seems to have a cult following. It might be good but is is THAT good??
Heh. Yeah, I does seem to have a cult following. And I'm a cultist. I currently have almost 10 #'s of it - probably close to 1/3 of my total propellant inventory. It's that good.
My three most used calibers in this order are: 38 Special; 44 Special; and 45 ACP. W231/HP-38 does really well in these three chamberings. So "cultist" may be a bit of a stretch - I have a lot of W231 because of what I shoot.
It is great stuff though. Really.
You have Bullseye. It's nearly as good. W231 is just a tick slower, giving it a little more wiggle room to build up velocities a bit. It also runs a touch cleaner. But other that that, I wouldn't say it's any better than Bullseye. I like Bullseye a lot. In fact, the only reason why I phased Bullseye out of my inventory is because I have chosen to use W231 (for the reasons mentioned above).
My oldest recipe - circa 1985 - is 45 ACP 5.0gn W231 under a 200gn LSWC. I'm sure I have loaded more of that recipe than any other - by far. 840 f/s through a full-size 1911. Talk about tried n true. That's it. I even have a seat die dedicated just for the 200 LSWC - no adjustment needed; just spin it in and go. In 45 ACP, W231 works with any bullet weight. It'll come up a little short in velocity pushing heavies. But if you're keeping it at range practice levels, it's fantastic.
I use W231 in pretty much all my 44 Special loadings. Save for the canister of Trail Boss I bought just to check it out. But once it's empty, it's back to the W231
I load more 38 Special than any other caliber. More than 90% of them is with W231. Okay, I'm in the process of phasing out AA2 from my inventory; but once that's gone, it's back to W231. I shoot mostly 148 DEWC's (plated these days - I don't deal with lead any more - I'm done scrubbing barrels
), and 125 plated FP's and jacketed HP's. All get W231. The only exception is my max velocity 125 HP's which get either BE-86 (neat stuff) or Power Pistol (absolutely phenomenal stuff).
W231 also works well in 9mm; particularly 115's. But will make good range ammo with 124's too.
W231 has frightened me with 357 Magnum. Using the book minimum, I got super flattened primers; case bulges, and very difficult extractions. I thought I did something wrong, so I made another batch with the same result. This was years ago using 125 HP's. I don't use W231 for any 357 or 44 Magnum application.
I've never tried it in 10mm Auto, and likely never will. It's just too fast.
So yeah, W231/HP-38 is remarkably good. In the autumn of '84, the guy behind the counter at my sporting goods store pointed at a then steel canister (or maybe aluminum?? Steel is ferrous) of Winchester 231 and told me to give it a try, so I did. Since that very day, I have never been out of W231. Never.