2
by wings
9 is fine. Arrows are still more than adequate for penetration, even practice points.
Until you start looking at hydrostatic shock, over 2000fps, bows are just as good at making holes as guns, and much more quietly.
My high school history teacher brought in our librarian to talk about Vietnam. Apparently he'd been special forces, and one of the things he brought was a Vietnamese-style crossbow. Looked like an English longbow mounted on a stock. He claimed that they could still penetrate sandbags at 100 yards with it, while the 5.56 would bounce off. Reinforced my early preference for archery. There are still some great B&W Army training videos doing similar comparisons online. Sure, KE=1/2mv^2, but momemum=mv, and an arrow carries far more.
Cheaper than NFA, too.