I would personally say yes, 63 grams of Triple Se7en is enough for Whitetail inside 70 yards. 63 grains of T-7 has about the same power as 70 grains of Pyrodex RS. I have personally shot a deer at just under 50 yards with 70 grains of Pyrodex RS and a .490 patched roundball.

Shot placement is always critical with every hunting situation but remember you're putting almost a half inch hole through vital organs of an animal. That size hole and the tissue damage it will do, will cause the death of that animal. Whitetail deer are thin skinned and not all that hard to poke a hole through.

Back in our country's early days when powder and ball was hard to come by, many times loads such as 50 grains of powder and a roundball were used to harvest deer. There are records of even smaller charges then that being used. These early pioneers were excellent trackers though, and I am sure that was all taken into consideration.

As long as you can place that shot at 70 yards everytime, I do not think you will have a problem harvesting a whitetail deer with that charge. I do not know how much more I would push the distance out of consideration to the animal alone, but for what you're planning, place that projectile and be ready to track if need be....