Lets be honest..you are probably not going to be buying 3N38 to use in 9MM unless you want high velocity. Am I right? Or you want to play in 9MM Major category..
4.5 OSP using Threaded barrel, which is slightly over 5". There is no book data on these rounds, so I ball parked a range for you to estimate results on...I would guess, just a guess, NOT A FACT, that maximum load for 3n38 with:
Speer 124 RN @ 1.150 OAL is probably around 7.2 then you are in +P area. Xtreme 147 RN @ 1.150 OAL? I would guess around 6.7 then you are +P area. Give or take a guess of like .3 ballpark. 3N38 EASILY makes MAJOR power factor, in possibly just +p area, guessing. As long as you can use long OAL such as 1.150-1.160 estimate. For 124 grain, it needs more, 7.8-7.9 would be needed if your barrel was like ~5.2" guessing, depending on brass capacity...147 is super easy.
Here are results:
Speer 124 RN: 7.0 grains = 1200 FPS/396 Energy PF: 149
Speer 124 RN: 7.3 grains = 1240 FPS/423 Energy PF: 154
Speer 124 RN: 7.6 grains = 1300 FPS/465 Energy PF: 161
Xtreme 147 RN: 6.5 grains = 1140 FPS/424 Energy PF: 168
Xtreme 147 RN: 6.8 grains = 1170 FPS/447 Energy PF: 172
Xtreme 147 RN: 7.1 grains = 1200 FPS/470 Energy PF: 176
1200 FPS in 147 grain? That is a hammer. But it kicked like a donkey. I never got kicked by a donkey, I just heard it hurts...
So to wrap this up...I can easily understand why 3N38 is popular with Major, its easy to make major, and its accurate. And widely available, because literally nobody would use it for "everyday" 9MM. Its way too slow.