Here's some classified information for getting top accuracy from HBWCs.
Try using a Lee Factory Crimp Die for the .38 Special (with seating stem removed) or Lee .38 Super Undersized Sizing Die for sizing your wadcutter brass. Expand sized cases with a Wadcutter Expander (available from RCBS) and taper crimp. You don't need much case tension with HBWCs.
I use Remington HBWCs but have gotten good results with the HBWCs from Magnus (they look like dead ringers for the Zero Brand).
Bullet: Remington 148 gr. HBWC
Powder: Alliant Bullseye 2.8 grs.
Primer: Federal 100 Small Pistol Match
Case: Remington Wadcutter
LOAL: 1.185
Comments: Cases resized using Lee Factory Crimp Die with seating stem removed and taper-crimped.
You can actually use unsized brass with the Remington bullets but I like to run them through a Lee Die.
A ten shot groups off-hand at 25 yards
I'm a mediocre shot who wears bi-focals so I must be doing something right!
Here's another one that shoots well.
Bullet: Magnus 148 gr. HBWC
Powder: VihtaVuori N310 2.6 grs.
Primer: Federal 100 Small Pistol Match
Case: Federal .38 Special
LOAL: 1.200