Hi everyone! I love creative weaponry. Been looking at the crazy Jeorg vids for a couple months, and finally when I saw the folding sling xbow decided I had to join the fun. I'm building a variation on that thing. (It's really a slingshot rifle by now, isn't it??) I'm using oak instead of plywood, and deploying items from home improvement megastores in the build. A Tornado 20 pound u-hook looks like it was designed for slingshots; the frame of a caster will function as a sear, a hinge stop will work as a trigger, etc. A couple of questions. First, has anyone measured projectile speed on a chrony? And second, what are the limits of rubber stretch? I want to use .58 lead, 280 grains, and want to reach "muzzle velocity" of 90 to 100 meters per second if possible. So the more I can stretch it the better, or so I imagine. Finally, a thing I learned using that ammo: a pair of opposing perpendicular splits with a razor knife make the hit even better. It deforms more readily on impact, thus transferring even more of its energy. And the sharp edges created by the razor knife help it dig into the target.