Making primers without certain licenses would probably also be construed as being illegal. You did not suggest that, I know. But a “black market” would probably not find a domestic source of contemporary primers (my point). Supplies for flintlocks might be possible, though.
There are also big bore air rifles up to .50 caliber that can penetrate 2 inches of wood at 100 yards. Some are fully automatic at 223 caliber.