Help with terminology and why I ask

[Wise_A]

I just found the Lee VMD table and am looking for the bulkiest powder that will work. With a 3" barrel I figure I'll need a fairly fast powder.

Looking at the VMD chart will get you nowhere, because the max load isn't the same. Which is sort've beside the point--at some point you have to simply develop and trust your technique, pay attention, and check your work.

1200 fps is a tall order for a 3" with a 158 (or even a 125). Plenty of powders will get you close according to book data. Universal gets you closest while still being happy, but I can't stand the stuff. No matter how hot I load it, no matter what the crimp, there's always some unburned powder in the case--maybe I got a bad lot.

I would go with Unique. Unlike some of the faster powders, it's very happy operating at Magnum pressures. It doesn't quite develop the same book velocities of some of the slower options, but I'd wager that it'll get better velocities out of the 3" barrel.

 

[jaymoore]

I've been loading 38 Spl and 357 mag cartridges with 3.5 gr of TB and 125 gr cast lead coated bullets. My Lee charger works good for that. Nice light load and fun to shoot. Shot 200 of them Wednesday. But, thinking ahead to when I run out of 158 grain/1200 fps factory loads. Wondering what powder to use for that. Can't get enough TB in the case for that. I just found the Lee VMD table and am looking for the bulkiest powder that will work. With a 3" barrel I figure I'll need a fairly fast powder.
Thanks for your assistance. I'm only asking questions here that I have not answered elsewhere. Took a long time to find the VMD table!

Some good points in the posts above, but it seems you are on the right track for safety and uniformity already!

For your factory equivalent loads, the usual recommendations in books other than the very useful Lee tome center around 2400, IMR4227 and WW296/H110. As also noted above, H110 isn't well suited for reduced loads, but is often a maximum performer. The other two powders are rather more flexible.

If you want maximum fill with less velocity and pressure, you will have to stray from most published data. So that may not be something you want to attempt for quite some time!

My current long range loads at medium velocity have focused around full cases (no compression) of either IMR4198 and reloder7. Unlikely you will find published data for those powders in .357, but it works quite well! (One related reference is in the Lee book under the 44-40WCF with 240gr bullets, but that's all I've found so far!)