I've settled into RMR 124 gr RN plated bullets, WSP, 4.2 gr HP-38, 1.125 OAL as my current standard round for now, while I experiment here and there with a few other bullets. Closing in on close to 4,000 reloads since I started this last fall. Have loaded close to a thousand of these, and they have loaded and shot with no problems, and are certainly accurate enough for skill level and purpose (IDPA).
I picked up two pounds of WSF, and have been experimenting with that powder and 115 gr FMJ from RMR, 1.120 OAL, S&B primers. Ran a ladder, and two test batches of 50 rounds each at 5.1 gr and 5.3 gr of WSF. A little snappier than 124 gr bullets, but seemed just as accurate, and the perceived recoil difference evaporated after the first couple of rounds. I'm going to load up the rest of my 500 round test batch at 5.2 gr and 5.3 gr WSF and see if they would be acceptable as a back-up to my standard RMR 124 gr RN.
Next up, I would like to try out some of the RMR 124 gr "Hard Core" Hollow Point rounds with WSF. These bullets plunked very short in my SP01 Shadow barrel: ten dummy rounds ranged from 1.0585 up 1.09 OAL, with 1.0645 to 1.0655 being the most common. Based on those results subtracting .010 - .015, I'm looking at an OAL of ~1.055. These bullets are .555 long, so seating depth would be .75 + .555 - 1.055 = .250. RMR states that their "Hard Core" plated can be loaded to mid-range jacketed, so looking at load data for something comparable (124 gr JHP with WSF), I see past threads in this forum on Precision Delta 124 gr JHP, 1.09 OAL, load ladder of 4.4 - 4.8 gr WSF (seating depth = .243); Montana Gold 124 gr JHP at 1.065 OAL with 4.7 or 4.8 gr WSF (seating depth .264). I haven't been able to find any WSF data with 124 gr JHP in any of the manuals that I have access to, but did some find some data for HP-38/Win 231: Lyman manual has Sierra 125 gr JHP, 1.075 OAL (seating depth = .222), 3.9 - 4.4 gr Win 231; 124 gr HAP, 1.069 OAL, 2.8 - 3.3 gr HP-38 (seating depth = .253).
Based on these comparable data points, I've convinced myself that 1.055 OAL isn't too deep, since I see other 124 gr JHP with very similar (or even deeper) seating depths. Looking for some confirmation/second opinions on a good load window: I'm thinking 4.3 - 4.7 gr WSF, working up in .1 gr increments. Am I thinking about this the right way? Anything I've overlooked? Does that seem like a reasonable load window?