Since I own several .357s I don't see much reason to shoot a lot of
+P 38s and I have some older Rem 158 gr LHPs that chrono at around
900 fps out of my 4" S&W 10-5. My experience with swaged bullets in
handloads has not encouraged me to load them hot so my +P 158 gr
handloads have been with cast SWCs. Original Win data for 231 stops
at 4.8grs for +P loads with a jacketed 158 gr bullet but pressure is
only barely +P at 17,200 psi. This reluctance to list loads anywhere
the +P limit of 20,000 psi seems to be typical of most manuals. My
top load of 231 has been 5.1 grs with a 158 gr cast SWC with Win
brass and mag primer. This is less than I have seen in some manuals
and I do believe that it is below the +P limit of 20,000 psi. I have
chronographed it in three of my model 10s with good velocity and low
ES as follows; 2" 10-5 vel=910 fps ES=12 fps, 3" 10-8 vel=982 fps
ES=20 fps, 4" 10-5 vel=1003 fps ES=14 fps. It's just a cast SWC
load but it seems like a pretty good one to me.