ChrisD, here is some data that I accumulated from this forum over the last year or so. Most of this, if not all, has come from a poster on this site that goes by the handle "boatbum101". I have tried a few of these loads with excellent success.
"I use the Zero & Remington HBWC's in my 52-2 & have not expierenced this problem .
I also trim cases to 1.145 but taper crimp to .368 - .369 .
I also use a heavier charge ie 3.1 - 3.2 W231 , 3.6 VV N340 or 2.9 AA #2 or VV N320 .
These group better in my gun than 2.7 - 2.9 BE , especially @ 50yds .
I'd go no more than 3.0 BE max with a 148 HBWC .
I must confess I like a little slower powder in 38 target loads . Hope this helps .
I learned that from Jerry Kieffer . That & preferred powders for 38 special accuracy are WST & W231 .
He's an outstanding 'smith & has done tons of load testing . N320 is pretty close to W231 but cleaner burning .
I've also had very good results from 3.6 N340 . 148 HBWC's demand a faster twist for ultimate accuracy .
PPC guns are usually built with 1 in 12 or 1 in 10 twist for that reason .
Slower S&W twist demands proper loading techniques & if followed can produce acceptible accuracy .
It's not unusal to see some " tipping " @ 50yds from S&W barrels .
I'm glad you were able to solve your problem . If you have them also try 2.7 WST & 3.1 - 3.2 W231 .
See attached 50yd targets shot offhand with my 52-2 & W231 / N340 loads .
My 52 groups best ( @ 50yds ) with 3.1-3.2 W231 ( depending on the lot of powder ) , followed very closely by 3.6 VVN340"
Again, most or all of this is boatbum101's data and suggestions. It did help me tremendously with a problem I had with the chamber leading on my Model 52.