I prefer to stick with the traditional 158gr bullet weight for the .38 Special, that is what the fixed sight service revolvers will be regulated for. I think that it's funny that most folks today think of the 158gr. bullet weight as a heavy weight for the .38 SPl and the .357 mag
A heavy weight bullet would be anything that is above 158gr. I like the Remington 158gr LSWCHP (+P) as it has a good track record, and it hits close to the sights of my S&W M10.
Dave T, you must have gotten ahold of a bad batch of ammo to get velocities that low from a 4" barrel. Here is some very thorough chrongraph tests done on various .38 SPL ammo.