The classic load of 2.7/2.8 gr Bullseye under a soft swaged HBWC in 38 SPL cases for use in 38 SPL chambers is a classic for a reason....accuracy. Just yesterday I pressure tested some Remington swaged (.360 diameter) HBWCs over 2.7 gr of Bullseye in my Contender test barrel and also accuracy/velocity tested that load in my old service revolver, a M15 with 5" barrel. W-W cases with CCI 500 primers were used. Target was at 50 yards and a Ransom Rest was used.
The pressure for a 10 shot test out of the Contender barrel ran 13,300 psi with with an ES/SD of 2,000/600 psi. The velocity ran 806 fps with an ES/SD of 29/10 fps. The 10 shot group was just under 2".
In the S&W M15 a 14 shot test gave 730 fps with an ES/SD of 44/11 fps. The 14 shot group went into 3.25".
The Contender has a 16" twist so the bullet holes were nice and round. The S&W M15 has an 18 3/4" twist and the group, especially those on the out edge of the group, showed some key holing. That was always the case with the HBWC loads in S&W barrels. Most PPC revolvers, back in the day, had 16" twist custom heavy barrels for that reason. Some also had Colt Python 6" barrels which had 16" twists put on S&W revolvers. We called those Smythons......
Back in the day I shot a lot of those Remington and Speer 148 gr HBWCs in my PPC revolver built on a S&W M10. However, with solid base WCs and DE WCs most used 3 gr of Bullseye. Those were the loads most everyone used.