When loaded properly, 148gr HBWCs are probably the most accurate bullets you can find. These bullets do have some quirks. First, they are the only bullets available where the nose is heavier than the base. Because of this, HBWCs are more sensitive to "spin rate" than other bullets. Spin rate is a combination of your rifling twist rate (typically 1:18.75 for a 38/357) and velocity. If HBWCs are not spun fast enough (velocity too low), they tend to lose stability and tumble (keyhole), which is traditional for all bullets. If they are spun too fast (velocity too high), they will also lose stability and tumble. This phenomenon is unique to HBWCs. The velocity range for best stability is between 700 and 800 fps.
Because Speer HBWCs are very soft (BHN 10) the skirt expands with chamber pressure and forces the bullet to seal tightly in the bore. This is good for accuracy and minimal bore fouling. If HBWCs are driven too fast, the skirt can separate from the body and remain in the bore. This is very bad because the obstruction can blow the gun up when another round is fired. If you stay within the 700~800 fps limits, you will never have a problem, however if you try to run them hot, you risk damage to your gun plus accuracy will be poor.
HBWCs have the aerodynamics of a brick so velocity and spin rate slow down a lot in short distances. At 25 yards, they will be very stable and not drop much but at farther distances, they drop like a rock and get unstable. It is not unusual for HBWCs to keyhole at 40 yards and will drop several inches so don't expect them to work well at extended distances.
To get the best performance from HBWCs, you need a light charge of very fast burning powder. This will generate enough chamber pressure to force the bullet to obturate without developing too much velocity. The best powder available for these bullets is Bullseye. 2.8 gr in a 6" revolver or 3.0 gr in a 4" will get you the best accuracy with minimal fouling. I have never tried Trail Boss because my manuals don't list loads for 148 gr HBWCs. If you can find a reputable load that will deliver the above velocities, it should work OK.
The proper way to load HBWCs is to seat the bullet flush with the case mouth then apply just enough crimp to remove the case mouth bell. Do not over crimp or the bullets will foul the bore. Because these bullets have a long case-to-bullet contact, there is no need for crimp at all but you do want to remove the case mouth bell so they will chamber properly. Lee FCD crimp dies are not recommended for soft lead bullets because they do a total case resize after the bullet has been seated. This will actually squish the bullets down from .358" to less than .357", which can also cause bore fouling.
For at least 30 years, the pet load for my 6" S&W Mod 14 38 Special has been a Speer 148gr HBWC with 2.8 gr of Bullseye. For my 4" 357 Mag revolvers, I increase the powder charge to 3.0 gr and get about the same velocity. These loads will blow the 10X ring out of 25 yard target.
