According to the Hodgdon data, with an AOL of 1.200 the following are the maximum for HS-6
230 grain lead is 8.0 grains
230 grain FMJ is 8.2 grains.
The data shown does not indicate a magnum primer or not so for safety I would assume a regular primer.
The rule of thumb is that a magnum primer may increase pressures by 10% and therefore reduce powder accordingly.
So IMO your loads using 7.8 are going to be very hot depending on the type of bullet that
you have used & the AOL of your load.