I looked in the Lyman #4 and the load I see is 31.0 grains, not 30. Although Blue Dot is a fluffy powder, one grain should not make that much difference but maybe so. In shotshell loading, you have to follow the recipies fairly closely or you won't get the correct stackup of components to achieve the correct crimp. Three possibilites:
1. You have 3" hulls, not 2 3/4. Compare them to some other fired hulls you have.
2. This was a 3" or 3.5" PF hull that was cut to 2 3/4. Either one would give a hull with a much lower basewad than the 2 3/4" PF. (Look at the basewad heights in the Lyman manual.)
3. Winchester changed their hull construction for their PF hulls. They also now have a "Universal" hull that is used in their promotional shells that is different than the PF hulls contained in the Lyman manual. They have a silver, I believe Aluminum case head. (You said you had highbrass, so these are probably not the same hulls.) When I find the "Universal" hull, I just discard them.
All my 00B hulls are Compression Formed, not Poly Formed. I suggest you section a hull and compare basewad height to the diagram of the WW 2 3/4" hull in the manual.