I am using 63 gr. of triple seven. Gun shoots great. But is this enough for whitetails inside 70 yards?
Yes... just make sure the powder is kept dry because you are at the bottom of the road for bullet speed/energy.
I would like to remind you thou.... what you have is a fast twist ML that's best suited for sabot/bullets. A similar trajectory load would be a 300 grain sabot/bullet with 75 grains.