The OAL confusion here comes from the fact that
Semi Wadcutters (SWC) have a
normal conical bullet shape and are loaded like normal bullets (i.e., 50% or more projecting well above the casing).
Plain old (i.e., "full") Wadcutters, on the other hand have no conical shape at all.
They look like 55-gallon drums and are loaded almost completely within the
case --
flush with its mouth.
This
drastically reduces internal powder volume and raises pressures for
whatever amount of powder is loaded.
Do not use loading manual data for semi wadcutters when loading for flush-seated full wadcutters.... even if the projectile weight is the same.
How to tell which-is-which for 38 Special:
Semi-wadcutter OALs are generally 1.55" (~ 40mm).
Full wadcutter OALs are much shorter:
- (1) totally even with the case mouth at 1.14" (29mm), or
- (2) just slightly above it in a crimping groove, 1.15" - 1.3" (30-33mm), ...
and are listed with
much lower powder charges.