I would certainly be interested in your results with the 125 JHPs.I have loaded/shot over a thousand 2.5g 700X loads in .38 Spl - most of them with 148g HBWC bullets where the MAXIMUM load is 2.5g 700X. Zero squibs. Those loads chrono at 660 fps with an average deviation of 21.
I have loaded 2.2g 700X behind the same bullets with mixed results. 2.2g gives 552 fps +/- 14 and shoot very well. The problem, however, is that when I load these with my Lee Auto Disk powder measure, I get large variations in the tiny charges of 700X using a disk cavity of .30cc, including a few squibs. So with my Lee Auto disk, a disk cavity of .34cc, throwing 2.5g 700X is very consistent, but a disk cavity of .30cc throwing 2.2g 700X is unacceptable.
I have never noticed any position sensitivity with 700X, but I have never specifically tested for it either.
Last night I loaded some test rounds with 2.8g 700X (all carefully weighed) and Zero 125g JHP bullets (real jacketed, not plated). I will shoot them later this morning and report those results.
Your 148 HBWC load with 2.5 gr of 700X is at the maximum, like you said. It's at the other end of the pressure spectrum from my 2.8 grain load with the 125 Berry's plated FP.
Your OAL length is much shorter with a HBWC load, giving less empty space in the case. Seems as though this difference could reduce any effect of position sensitivity.