What powder measure were you using for the loose powder loads? My TC U-View measure throws lighter charges than the scale indicates.
Hodgdon says two 50 grain T7 pellets are equal to 100 grains volume equivalent of black powder (they don't state a black powder grade, but one would assume it's FFg). If I set my TC U-View at the 100 grain mark and fill it with GOEX FFg, the load weighs only 89.5 grains on my RCBS powder scale.
So when I shoot a 100 grain measure of T7 using the TC measure, I am actually shooting less than 90 grains "equivalent" of black powder.