i emailed winchester about that and they limit 100 grains of loose powder mainly due to anything more would be a waste and not give a complete burn of powder. They also told me you can shoot up to 130 grains pyrodex/blackpowder safely with no issues. My normal load is 120 grains pyrodex RS with a 295 grain powerbelt. Last year i cut my charge down to 90 grains when i was using the 385 great plains bullet. Mainly just to tame the recoil. Ive never used triple 7 so i dont know how those loads work out. I prefer pyrodex RS. Ive shot up to 170 grains loosepyrodex rs with 295 powerbelt and it worked perfectly, also made a nice sparkler show of burning powder. So the 100 grains max limit they say in the book is mainly there for you so you dont waste powder. Enjoy the rifle.