Assuming the OP is not trolling, a couple of points to make are:
It doesn't matter if the 148-grain bullet is DEWC or HBWC, provided they are seated nose-forward and are made of the same material and are seated to the same COL, the extra space taken up by the greater length of the HBWC is given back as space in the hollow base, so the net powder space is the same. For the reverse HB wadcutter, if you seat it all the way down to flush with the case mouth, the powder space will be smaller and pressure will increase significantly. To make pressure match, the HB-forward load needs to be seated to stick out of the case by an amount equal to the difference between its length and the DEWC's length.
If you look at Hodgdon's data for wadcutters in .38 Special and .357, for 231 the .357 max load is actually smaller. I attribute this to the primer unseating the bullet in the .38 Special so that more space actually results. I emailed Hodgdon about this long ago and the came back that this is what their ballistic technician said the test results actually showed. So the 10% rule may not apply in small spaces. It depends on the powder.
If there was a bunch of unburned Bullseye in the gun, you had some kind of ignition failure resulting in a super low-pressure event. I would not expect that with Bullseye. Make sure it is dry. I would make sure to have some crimp on the bullets, though. If your sizing die is only sizing the cases marginally or if they are work-hardened enough from repeated reloadings to tend to spring back out a bit after resizing and you didn't put enough crimp on the case, then the bullet popping out under primer pressure and before the powder really gets burning is a possibility. Also, if your bullets are wax lubricated and the cartridges got hot in the car, the lesser possibilty of wax contaminating the powder also exists. Especially with HB bullets store nose-down, putting the powder into that waxy hollow. You can sharpen a used case with a chamfering tool and use it to cut discs from paper and put one over the powder before seating the bullet to prevent that effect.