If you do a search, the 135gr. Speer GD performs well for the .38 special snubys (sic)
Yes, the Speer 135gn GDHP SB is arguably THE best bullet for low velocity expansion. I started searching for them in '13 - during the big shortage; great timing. Finally, Midway had them and I bought 500 of them. I've since done work ups with 38+p and 357 Mag. I haven't done expansion testing. But I have chronographed the +P in my 1.875" S&W Model 60; and have gotten plenty of velocity for expansion (as advertised, anyway).
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I don't know if the following exceeds +P pressures, but I suspect it's close.
Using BE-86 - because it seemed logical to use a flash suppressed propellant; and it's also an ideal burn rate for the pressures involved.
Alliant's site show both the 130gn FMJ and the 125 JHP maximum charge at 6.1 grains. In my work up, I settled on 6.0gn for my 135 GDHP SB's. I chronographed two different batches and got the following from 10-round samples:
890 f/s and 909 f/s through my snubbie.
(961 f/s and 941f/s respectively though a 4" bbl - odd that the latter test - compared to the former test - yielded a lower velocity through the 4" and higher through the 2".)
There were no signs of excessive pressure. Recoil was quite firm but plenty controllable for this old guy with small arthritic hands. According to the Speer manual, this is plenty of velocity for expansion. Of course, the real world may tell a different tale. But there's some info I hope to be helpful.