A few loads from the Hornady Reloading manual for the 124gn GDHP:
HS-6: 6.4gn - 6.8gn
Win 231 4.4gn - 4.8gn
Titegroup 4.1gn - 4.4gn
Clays 3.5gn - 3.7gn
Personally, I prefer the Clays. Not International or Universal, just the standard Clays powder. It makes my .45 so sweet to shoot. Love it! And on top of that, its cheaper, and you use less of it, so you stretch your dollar farther.
I just did a test with Titegroup and 9mm GDHP, and I wasn't so happy with the results. I'm sticking to Clays.
If you want velocity, but if you are just plinking " Why use JHP ? "
I have some good plinking loads with 115 and 124 gr FMJ's. Would like to get a JHP load that I can work up to something closer to my self defense ammunition for practice.
Load up batches of 10 pcs in X, X+.2, X+.4, X+.6 and get with me and we can Chrono some to determine velocity