I have shot 38s and 357s for a couple of decades, but when it came to shooting 38 Special cast bullet reloads in my 357 magnum revolvers I usually stuck to semi-wadcutters, almost always 158 grain. Lately I started reloading and shooting 148 grain bevel base wadcutters from the Hardcast Bullet Company in my GP-100 using Hodgdon Titegroup powder and CCI primers. At first, things seemed okay, but as I increased the powder charge, it turned out that I was shaving part of the bullets in the cylinder! This had never happened with any cast bullet before of any powder load (this being 38 Specials shot in 357 Mag chambers).

It could be a couple thing have you had the handgun checked out to see if it is out of time?
Check the barrel and see if there is any nick or burnt carbon built up in the area of the gap or excessive gap?
make sure you get enough bell in the case when you seat the bullets you could be shaving some lead there.

Ok, will check; it does not occur with other lead bullets, just this one. I have heard of people having their chambers and bores slugged for exact measurements, I just have never perceived the need to. Thanks, will check on the timing.

i'd look at those hard cast boolits for a diameter variation.
there is a huge difference between a 357 diameter and a 358 diameter bullet.
especially when the smaller one is stupid hard like 16-18 bhn.