WST on .38 special

[mamigor]

In Modern Reloading Second Edition by Richard Lee I read that "When you change to a lighter bullet, with the same powder more amount is allowed and the pressure remains nearly the same"

But I went into Hodgdon's official site and found that on a .38 special less WST powder is needed for the lighter bullet.

Bullet Weight (Gr.) Manufacturer Grs.
148 GR. HDY LHBWC Winchester 2.5-2.8
158 GR. CAST LSWC Winchester 3.3-3.7

and on Mr.Lee's Book it is said on a 148 Grain Wad Cutter bullet with WST it goes from 2.5 gr to 2.7 gr
and on a 158 grain Lead Bullet with WST it goes from 3.3 grs to 3.7 grains, they're both exactly the same.

Can somebody help me understand why does this happen?

 

[Ledhore]

Wadcutters are seated much deeper into the case, leaving less volume for the powder. WST is a nice powder for .38 spl. I use 3.5 grains with the Lee round nose flat point, which weighs 162grains with my alloy.

 

[mamigor]

Thank you, I cast my own .38 special lsw in an old lyman's bullet mold and I use ww and they usually weight over 160 gr.
Thank you very much

 

[evan price]

The hollow base wadcutter is typically seated flush to the end of the brass. The entire bullet is in the case. Less room for powder gas to expand, less powder needed. Any time you see a HBWC or a 148-gr WC assume it is one of these unless otherwise noted.

 

[Walkalong]

Compare the same type 158 and 125 Gr bullets in .38 Spl and you will see what he meant.

As posted, the WC is a case by its self due to how deep it seats and how light it is usually loaded.