I find that the lowest 38 +P loads work well with 125gr JSP bullets. I just put together 200 +P's using said bullet over 4.5gr Bullseye, in +P brass, of course. Very accurate! And some of the older data lists this charge right at the top end of 38 SPL. Which kind of goes along with it being the lowest +P load listed in today's books. COL=1.440".
I also have had similar results with Berry's 125gr plated HP's and the same charge. COL=1.445"-1.450"