If you used a 180 grain bullet and only 50 grains of powder would this be enough to penatrate a deer enough to kill it.

That is a very hard question to answer. It would depend on the distance, whether you hit bone going in, the density of the bone, etc. I would think if the rangewas close like 50 yards and under, I see no reason why it would not penetrate a deer. I am guessing of course.

I have a book by Don Davis that he states a favorite load for his friend's .50 caliber flintlock was 50 grains of powder and a roundball. His theory was, the ball would enter, lodge in the vitals and all the energy of the ball would stop right there. A roundball weighs 177 grains so you are basically shooting weight in that load.

I am guessing this is for a young person or someone recoil sensitive. I personally would not recommend that load to anyone, but then I also make it a point to not tell anyone what to shoot or hunt with. That is a personal decision they have to make.

Good question. A lot would depend on bullet construction. As cayugad said, a 177 grain PRB can certainly kill a deer at moderate velocity and appropriate range, but I suspect your tracking skills would need to be pretty good with something like a double lung shot. I wouldn't shoot a deer with aload like that myself, except maybe a neck shot from a tree stand at bow ranges.

Anybody know what the velocity would be?