Sounds like you are getting decent advice in this thread... and my advice differs a little bit. Doesn't mean I'm right and they are wrong, and doesn't mean the opposite either. Just take my experience along with the other advice you've gotten and keep it in mind.
I've loaded thousands of 125gr Berry's 9mm bullets. Typically I use the 125gr RN, recently I've taken to using the flat point.
In both cases, I load these to full 9mm jacketed loads. I don't load them -HOT- but I don't run them like they are soft lead.
I don't have W231 and haven't ever used it, but you can compare a couple of my favorite loads to published max (which varies by source) to get an idea of how I load them:
With Power Pistol, I load them to around 6.0 grains at a COAL of 1.158"
I've loaded them higher, but have settled on 6.0 grains.
With Universal, I load them to 4.7 grains at the same COAL.
With Bullseye, I load them with 4.4 grains at the same COAL, but it's been a long time.
I use Berry's plated bullets in 7 handgun calibers. The one thing I will NOT do is to be bashful with them. These are not lead bullets and if you go too light, pounding them out of a bore because you stuck one is no fun whatsoever.
Attention Brass rats and other reloaders: I really need .327 Federal Magnum brass, no lot size too small. Tell me what caliber you need and I'll see what I have to swap. PM me and we'll discuss.