HP38 and W231 would be prime candidates for 9mm powder. I was, in my reloading days, a die hard Hodgdon Universal Clays guy for .40 and 9mm. But I'd use either of those 2 powders you named. Find the longest OAL you can load and fit in your magazine. By that, I mean get some sized and flared brass ready (no primers) and start at the longest OAL by caliber (9mm round nose is 1.145" btw). See if you can lock your slide back, insert a magazine with 1 of those inert rounds, and hit your slide lock lever and let the spring send it home. If it feeds it, you're good. Then start at the low end of the charge range and make 10. Bump up a little on powder and make 10 more. So on and so forth. Range test them for accuracy at 10 or 15 yards. Use a chronograph if you got one. Whichever shoots the tightest group, use that. Shortening your OAL (overall length) has a similar effect of increasing powder charge because you are decreasing available case volume. If you are using flat nose 9mm or hollowpoint, you have a little more work to do on measuring OAL. And here's how you do it. Take a prepped case, and measure it's length with a caliper. Write it down. Call it measurement A. Take the flat nose or hollowpoint projectile and measure its length. Write that down. This is measurement B. Set your seating die in the press and try to seat the bullet. Take it out, and measure its overall finished length. With this measurement, subtract the length of the case, measurement A. Write down this result, it is measurement C. Take measurement B and subtract C, and you have your seated depth, D. Repeat this process for your round nose load, and tailor your seating die so that your flat nose round has the same depth D. With the same powder load, they will have the same operating pressure. With that process, you can change bullet type and generally retain all the performance of the standard round nose. With that said, the flat nose usually has more bearing surface and will probably be a more accurate round. Sent from my SM-A516U using Tapatalk