Semisane
100 grains Triple 7 FFG = 77.8 grains weight.
You must have a prety decent set of scales.... 100 grains of T7-2f is suppose to weigh 77.7 grains - hence the name Triple 7
And as cayugad says it can change a bit from lot to lot - or depending on the moisture your present bottle has absorbed after it was opened...
I have never gotten into weighing charges, cause I am not shooting paper for money, and the fact that 5 grains usually makes less than 1% difference.